International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 3(8), 26-35, August (2014) Int. Res. J. Environment Sci. International Science Congress Association 26 Biomonitoring in Lentic Ecosystems of Irongmara, District Cachar, Assam, India, with Special reference to Aquatic Insect communityBarman Bijita, Gupta Priti, Choudhury Dharitri, Dalal Arpita and Gupta Susmita Department of ecology and Environmental science, Assam University, Silchar-788011, INDIAAvailable online at: www.isca.in, www.isca.me Received 20th June 2014, revised 15th July 2014, accepted 18th August 2014 AbstractThis paper represented a preliminary three months data on the aquatic insect diversity of two ponds, one private property pond and one community pond of Irongmara village, district Cachar, Assam. The communitypond (pond1) was characterized by market and household waste disposal site and the privatepond (pond2) was characterized by a community fishery. A total of 16 families belonging to 5orders from pond 1 and 9 families belonging to 4 orders from pond 2 were recorded. The insect order Diptera was found to be abundant and dominant in pond1, while in pond2 the order Hemiptera was found more abundant and dominant. Dissolved oxygen of water on pond1 was found very low with high Free-CO and Electrical Conductivity while in pond2 the dissolved oxygen was found in good concentration with low Free-CO and Electrical Conductivity. Different biomonitoring scores were computed to see the water quality of the ponds and statistical analyses were done to find the relationship of environmental variables with insect density and family richness. The present study compared the water quality of the two types of ponds and concluded that the authorities, management and users should come forward with protective measures to save the ponds from deterioration. Keywords: Aquatic insects, hemiptera, diptera, pond, environmental variables. IntroductionA pond is a natural or man-made standing water bodysmaller than a lake and contains shallow water with marsh, aquatic flora and fauna. A pond is a feature of many landscapes and it contribute the mass of regional freshwater biodiversity1,2. Though they are small in size, they are rich in biodiversity and often act as biodiversity ‘‘hot spots’’ within the region or landscape. The pond system also shows greater variation in biotic and environmental variables than rivers and lakes. Major changes in environmental variables in a pond by anthropogenic activityinclude mainly changes in physical habitat and changes in chemical properties of the water. Habitat changes include water level decreases, increase of sedimentation, and decrease of depth. Change in water quality of pond includes eutrophication and toxic chemicals concentration increase. Aquatic insects were used as new tool to monitor these environmental impacts and changes in water.Because of their importance in nutrient cycling, inresponding to the changes in the environmental factors of waterand pollution sensitivity they are used widely as biomonitoring agent4-7. The study area Irongmara village has increasing trend of construction of buildings by draining and filling the house hold ponds or community ponds which have been serving the locality so long. The village with increasing population is also facing tremendous problem of solid waste disposal where often ponds are used as disposal site. Again there are many fishery ponds which are less subjected to pollutants or solid waste disposals. Taking all these facts into account, two ponds of Irongmara, one from market area and another fishery pond from residential area were selected to evaluate their water quality status using aquatic insects. It is thought thata few ponds which are still there in the urban setup are to be conserved for the betterment of the residents of that area. Material and Methods Study area: The Cachar district has an altitude of 26 – 27 m above MSL and 24- 25N latitude; 9215 - 9315 East Longitude. Irongmara, a village developed into township is very close to Assam University campus, Silchar, Cachar. Mean annual rainfall of this area is 2954 mm (Data recorded at Silcoorie Metrological Station).The temperature regime of the area shows that the maximum temperature ranges from 35.23C to 27.12C. The minimum temperature ranges from 25.53C to12.2C. Two ponds from the village, one community pond (pond1) and one private property pond (pond 2) were selected for this study. Thepond1is the common property of people staying in the area and the pond 2 is the private property of a villager. The descriptions of the sites of the two ponds are given in the table-1. Aquatic insect and Water quality: Two sampling sites, site 1 and site 2 from pond 1, and site 3 and site 4 from pond 2 were selected. The study was conducted during January to April, 2014 with five visits at each pond in regular intervals. Aquatic insects with three replicates from each site were collected by International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(8), 26-35, August (2014) Int. Res. J. Environment Sci. International Science Congress Association 27 kick method with a circular net (mesh size 60m) for a unit of time8,9. Three drags constituted a sample. Collected insects were immediately sorted and preserved in 70% alcohol. They were later identified using a Moticstereo zoom Microscope and Magnus stereozoom Microscope with the help of standard keys10-14. Water from the same sites were collected in replicates and water parameters like air temperature (AT), water temperature (WT), transparency (TR), pH, electrical conductivity (EC), dissolved oxygen (DO), free carbon dioxide (F-CO), total alkalinity (TA), nitrates and phosphates were estimated with standard methods15,16. Data Analyses: Average Score Per Taxon (ASPT) and Biological Monitoring Working Party (BMWP) were calculated followingstandard literature17. The BMWP score is obtained by summing the individual scores of all families present. Score values for individual families reflect their pollution tolerance18. The Average Score per Taxon (ASPT) is calculated by dividing BMWPscore by the total number of scoring family. Stream Invertebrate Grade Number- Average Level (SIGNAL) scoring system for macroinvertebrate was calculated19. Statistical analyses were done using software SPSS 16. Results and Discussion Aquatic Insect and their relationship with water variables: Several studies in the water quality and aquatic insects were done in India and also Barak Velly20-23. The present study revealed the aquatic insect orders and families recorded from two different ponds. All total5 orders and20 families were recorded from the two ponds. Five orders viz., Hemiptera, Odonata, Ephemeroptera, Diptera and Coleoptera from pond1 and four orders- Hemiptera, Odonata, Diptera, and Coleoptera from pond 2 were recorded. 16 families were recorded from pond 1and 9 families from pond 2. Five families were found common in the two ponds (table-2 and 3). In pond 1, the total number of insects was found to be highest in site 2, visit 2 and lowest in site 2 visit 4. In site 3 of pond 2, the total no. of insects was found to be highest in visit 4 and lowest in visit 2 (figure- 2). Table-1 Morphometry and description of the two ponds POND GPS Location Area (m 2 ) Vegetation Type Pond 1 Site 1 24 o 41  15.67 N 92 o 4433.25 E 783 Tree line, Grasses, Shrubs Mangiferaindica, areca nut,Combretumpilosum, Cynodondactylon, Psidiumguajava, Alocasiamacorrhiza, Hibiscus rosa-sinensis, etc.) Domestic disposal pond Site 2 244115.74N 92 o 4433.65E Pond 2 Site3 24 o 41  17.75  N 92 o 4417.55E 1482 Trees, Bamboo clump, shrubs Solanammyriacanthum, Cleome gynandra, Cynodondactylon, Melastomamalabathricum, etc.) Fishery Site 4 24 o 41  16.96N 92 o 4416.92E Figure-1 Map of India showing position of Assam followed by Map of Assam showing the Cachar district followed by map of Cachar showing Irongmara village followed by satellite imaginary of Irongmara village showing the two studied ponds International Research Journal of Environment Vol. 3(8), 26-35, August (2014) International Science Congress Association Total number of aquatic insects in different sites of two ponds in different visits Distribution of different aquatic insect familiesin the two sites of Pond 1 during five visits Order Family V 1 Hemiptera Naucoridae + Gerridae + Vellidae + Mesoveliidae - Corixidae + Aphididae - Coleoptera Elmidae + Dytiscidae + Hydraenidae - Hydrophilidae - Noteridae - Diptera Chironomidae + Culicidae + Simuliidae - Odonata Coenagrionidae + Ephemeroptera Baetidae - Distribution of different aquaticinsect families in the two sites of Pond 2 during five visits Order Family V 1 Hemiptera Gerridae Veliidae Hydrometridae Notonectidae Coleoptera Chrysomelidae Stephylinidae Odonata Coenagrionidae Diptera Chironomedae Culicidae Environment Sciences_______________ _________________________ International Science Congress Association Figure-2 Total number of aquatic insects in different sites of two ponds in different visits Table-2 Distribution of different aquatic insect familiesin the two sites of Pond 1 during five visits Site 1 V 1 V 2 V 3 V 4 V 5 V 1 V 2 + - - - - - - + - - - - - - + + + + + - + - - + - - - + + + - - - + - - - - + + + - + - - - - - - + - - + - - - - - + - - + - - - + + - - - - - - - - - - + + - + + + + + - - + - + - - - - - - + - + + - + - + + - - - - - + - Table-3 Distribution of different aquaticinsect families in the two sites of Pond 2 during five visits Site 1 V 1 V 2 V 3 V 4 V 5 V 1 V 2 + + + + + + + - + - + + - + - - + - - - - - - - + - - - + - - - - - - - - - + - - - - - + + - + - + + + - + + + - - - - - + + _________________________ ______ ISSN 2319–1414 Int. Res. J. Environment Sci. 28 Total number of aquatic insects in different sites of two ponds in different visits Distribution of different aquatic insect familiesin the two sites of Pond 1 during five visits Site 2 V 3 V 4 V 5 - - - - + - + + + - - - - - - - + - - - - - - - - + - - + - - + + + + + - + - - - - - + - + - - Distribution of different aquaticinsect families in the two sites of Pond 2 during five visits Site 2 V 3 V 4 V 5 + + + + + + - - - - - - - - - - - - - - - + + + + - + International Research Journal of Environment Vol. 3(8), 26-35, August (2014) International Science Congress Association In both the sites of pond 1, the density of Hemiptera was found to be highest in all the visits, while density of Odonata was found lowest in site 1, visit 4 (figure- 3). In site 3, Diptera showed highest density in visit 1 and visit 3 followed by Hemiptera. In rest of the visits Hemiptera had highest density followed by Diptera. In site 4 the density of order Hemiptera was found to be highest in all the visits except visit1 where Density of different orders of aquatic insects in two sites of Pond 1 during five visits Density of different orders of Environment Sciences_______________ _________________________ International Science Congress Association In both the sites of pond 1, the density of Hemiptera was found to be highest in all the visits, while density of Odonata was In site 3, pond 2 order showed highest density in visit 1 and visit 3 followed by Hemiptera. In rest of the visits Hemiptera had highest density followed by Diptera. In site 4 the density of order Hemiptera was found to be highest in all the visits except visit1 where Diptera had high density (figure-4) . of aquatic insects showed significantpositive correlation with DO and significantnegative correlation with nitrates (table At pond 2 site3, density of insect showed significant positive correlati on with depth, whereassignificant negative correlation with pH and phosphates (table-5). Figure-3 Density of different orders of aquatic insects in two sites of Pond 1 during five visits Figure-4 Density of different orders of aquatic insects in two sites of Pond 2 during five visits _________________________ ______ ISSN 2319–1414 Int. Res. J. Environment Sci. 29 . At pond 1, site2, the density of aquatic insects showed significantpositive correlation with DO and significantnegative correlation with nitrates (table -4). At pond 2 site3, density of insect showed significant positive on with depth, whereassignificant negative correlation Density of different orders of aquatic insects in two sites of Pond 1 during five visits aquatic insects in two sites of Pond 2 during five visits International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(8), 26-35, August (2014) Int. Res. J. Environment Sci. International Science Congress Association 30 Table-4 Significant Pearson’s Correlation coefficient matrix of different physico-chemical parameters with insect family richness and insect density in Pond 1 Sites Depth (cm) Air temperature (°C) Water temperature (°C) Transparency (cm) Dissolved Oxygen (mgl-1) Total Alkalinity (mgl-1) Nitrates (mgl-1) Site 1 Water temperature (°C) 0.525* 0.885** - - - - - - Dissolved Oxygen (mgl-1) 0.824** - - - - - - - Free-CO 2 (mgl - 1 ) - -0.808** -0.761** - - - - - pH - - - -0.515* - - - - Total Alkalinity (mgl - 1 ) 0.856** - - - -0.661** - - - Electrical Conductivity (mS/cm) 0.895** - 0.527* - -0.814** - 0.691** - Nitrate (mgl - 1 ) 0.668** - 0.663** - -0.583* - 0.551* - Site 2 Transparency(cm) -0.524* - - - - - - - Dissolved Oxygen (mgl - 1 ) - - - 0.853** - - - - Free-CO2(mgl - 1 ) - - -0.638* - - - - - Total Alkalinity(mgl - 1 ) - - - -0.519* -0.625* - - - EC (mS/cm) - - - -0.636* - - - - Nitrate(mgl - 1 ) - - - -0.930** -0.852** - 0.538* - Phosphate(mgl-1) - - 0.829** - - 0.702** -0.526* - Density(no./unit time) - - - - 0.660** - - -0.561* *. Correlation is significant at the 0.05 level (2-tailed), **. Correlation is significant at the 0.01 level (2-tailed). Table-5 Significant Pearson’s Correlation coefficient matrix of different physico-chemical parameters with insect family richness and insect density in Pond 2 Depth (cm) Air tempe-rature (°C) Water tempe-rature (°C) Dissolved Oxygen (mgl-1) Free-CO(mgl-1) pH Electrical Conductivity (uS/cm) Phosphat (mgl-1)e Density (no./unit time) Site 3 Air temperature(°C) 0.693** - - - - - - - - Water temperature(°C) - 0.716** - - - - - - - pH 0.742** - - - - - - - - Electrical Conductivity(mS/cm) - - - 0.565* - 0.542* - - - Nitrate(mg/l) -0.551* 0.650** - - - 0.631* - - - Phosphate(mg/l) - - - 0.565* - - 0.678** - - Density(no./unit time) 0.578* - - - - 0.521* - -0.559* - Family richness - - 0.577* - - - - - 0.628* Site 4 Water temperature (°C) - 0.884** - - - - - - - Total Alkalinity (mgl-1) - - - - 0.603* - - - - EC(mS/cm) - 0.836** 0.685** - - - - - - Nitrate(mgl - 1 ) - - - - - 0.593* - - - Phosphate(mg/l) - - 0.603* - - - - - - *. Correlation is significant at the 0.05 level (2-tailed).**. Correlation is significant at the 0.01 level (2-tailed). International Research Journal of Environment Vol. 3(8), 26-35, August (2014) International Science Congress Association In pond 1 site 1, the relative abundance of family Veliidae was found highest followed by Aphidae and Chironomidae in all the visits except visit 1, where Corixidae was relative than others. In site 2, Corixidae and Chironomidae were found equally abundant in visit 1, while in the rest of the visits the relative abundance of family Veliidae was found highest than Relative abundance of aquatic insect families in two sites of Pond 1 during five visits Relative abundance of aquatic insect families in two sites of Pond 2 during five visits Environment Sciences_______________ _________________________ International Science Congress Association In pond 1 site 1, the relative abundance of family Veliidae was found highest followed by Aphidae and Chironomidae in all the visits except visit 1, where Corixidae was relative ly abundant than others. In site 2, Corixidae and Chironomidae were found equally abundant in visit 1, while in the rest of the visits the relative abundance of family Veliidae was found highest than that of other families (figure- 5). In pond 2 site 3, fa Chironomidae was found relatively high in abundance in visits 1,3,5 and Gerridae was highly abundant in visits 2, 4. In site 4, Chironomidae in visits 1,5 and Gerridae in visits 2,3,4 were found relatively more abundant than others (figure Figure-5 Relative abundance of aquatic insect families in two sites of Pond 1 during five visits Figure-6 Relative abundance of aquatic insect families in two sites of Pond 2 during five visits _________________________ ______ ISSN 2319–1414 Int. Res. J. Environment Sci. 31 5). In pond 2 site 3, fa mily Chironomidae was found relatively high in abundance in visits 1,3,5 and Gerridae was highly abundant in visits 2, 4. In site 4, Chironomidae in visits 1,5 and Gerridae in visits 2,3,4 were found relatively more abundant than others (figure - 6). Relative abundance of aquatic insect families in two sites of Pond 1 during five visits Relative abundance of aquatic insect families in two sites of Pond 2 during five visits International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(8), 26-35, August (2014) Int. Res. J. Environment Sci. International Science Congress Association 32 Abundance and density of families belonging to the orders like Hemiptera, Coleoptera and Diptera throughout the study period in both the ponds indicated that only stronger and tolerant ones were able to survive. Patraet al. also found the high abundance of Hemiptera, Coleoptera and Diptera in the Santragachi Jheel Lake, West Bengal, India24. Physico-chemical variables of water: The composition and concentration of physico-chemical variables of water vary seasonally, daily or even hourly. The composition and distributions of organisms and the physico-chemical properties of water of any aquatic system are related to each other and also influenced by each other25. The physico-chemical properties of water of pond 1 and pond 2 are represented in the table-6 and table-7 respectively. The pH of pond 1 ranged from 6.89 to 7.74 and pond 2 ranged from 6.04 to 7.8. The pH range of both the ponds was much comparable with the results of previous study on 5 shallow ponds of Barak valley, Assam, North East India which revealed the pH range of 6.33 to 7.4326. Various biological activities in a system change the pH of water. The EC of water represents the availability of free ions such as nitrates, chlorides and bicarbonates in the water25. In the present study, the range of EC at pond 1 was 0.36 mScm-1 to 0.49 mScm-1 and the range at pond 2 was 0.0482 mScm-1 to 0.106 mScm-1. The EC of pond 1was found higher than pond 2 in all the sites and visits. Thus at pond 1 the input of organic and inorganic waste may be the cause of high EC27. Table-6 Physico-chemical properties of water of two sites of Pond 1 during five visits (Mean ±SD) Water variables Site 1 Site 2 Visit 1 Visit 2 Visit 3 Visit 4 Visit 5 Visit 1 Visit 2 Visit 3 Visit 4 Visit 5 Depth (cm) 11.5± 1.32 11.33± 1.04 11.5± 0.79 20.56± 5.50 27.36± 1.02 38±3 37.66± 2.08 36.33± 3.78 45.83± 5.55 41.4± 9.3 Air temperature (°C) 19±2 25.33± 1.52 24.33± 0.57 23.66± 1.52 25±1 24.13± 4.22 26.66± 1.15 24±1 25.66± 0.57 24.66± 0.57 Water temperature (°C) 16.33± 1.52 20.33± 1.52 21.33± 1.15 21.33± 1.15 22.33± 0.57 16.33± 1.52 22.33±1.15 21.33±1.52 23±1 21.33± 0.57 Transparency (cm) 8.08± 1.77 7.66±1.65 8.06± 1.53 7.96± 1.59 7.26± 0.41 30.66± 2.92 28.3± 3.46 36.33± 2.51 8.76± 1.05 6.46± 0.404 Dissolved oxygen (mgl-1) 0.7±0.2 0.8±0.1 0.8±0.1 0.38± 0.07 0.26± 0.26 0.5±0.1 0.866± 0.057 0.86± 0.05 0.15± 0.25 0±0 Free CO(mgl-1) 22.66± 1.52 8.66± 5.77 8±1 9.33± 0.57 11±2 11.66± 1.52 8.66± 0.057 7.33± 0.57 8.33± 0.577 9.66± 1.52 pH 7.766± 0.064 7.55± 0.317 7.76± 0.06 7.56± 0.14 7.71± 0.26 6.89± 0.59 7± 0.101 7.87± 0.03 7.50± 0.179 7.74± 0.06 Total alkalinity (mgl-1) 92.66± 2.08 90±7.81 94.33±0.57 96.33±3.78 132.66± 3.05 118.33±16.25 95± 2.64 93.33± 0.57 103±5.56 131.3± 1.52 Electrical conductivity (mS/cm) 0.36± 0.009 0.366± 0.02 0.37±0.01 0.48±0.01 0.48± 0.003 0.433± 0.086 0.417± 0.067 0.38± 0.005 0.491± 0.004 0.461± 0.02 Nitrate (mgl-1) 0±0 0±0 0.3±0.12 0.355± 0.03 0.372± 0.01 0±0 0±0 0.036± 0.037 0.376± 0.05 0.499±0.01 Phosphate (mgl-1) 0.084± 0.051 0.391± 0.019 0.02± 0.009 0.41± 0.008 0.262± 0.01 0.065± 0.034 0.475± 0.01 0.44± 0.06 0.382± 0.01 0.358± 0.05 International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(8), 26-35, August (2014) Int. Res. J. Environment Sci. International Science Congress Association 33 Table-7 Physico-chemical properties of water of two sites of Pond 2 during five visits (Mean ±SD) Water variables Site 3 Site 4 Visit 1 Visit 2 Visit 3 Visit 4 Visit 5 Visit 1 Visit 2 Visit 3 Visit 4 Visit 5 Depth (cm) 34±3.60 36±2.64 37±2 44±2.64 43.33± 4.04 30.66± 1.52 32±2.64 30±3.60 48.6±3.21 32±2 Air temperature (°C) 29.33± 0.57 25.66±0.57 25.33±0.57 23.3±0.57 22.66±1.52 28.33±3.05 24.33± 0.57 25±1 24±1 23±1 Water temperature ( °C) 24±2.64 23±1 23.33± 0.57 21.3±0.57 19.33±1.52 25±1 21.33± 0.57 22±1 21.3±0.57 19±1 Transparency (cm) 25.16± 2.56 26.33± 2.34 26.33± 1.52 26.3±2.30 26.96±4.27 25.83±1.89 27.33± 1.52 26±1.73 27.7± 1.58 25.3± 1.21 Dissolved oxygen (mg l-1) 4.75± 0.56 6.08± 0.58 5.42± 0.01 5.34± 0.127 5.21± 0.11 5.16± 0.152 5.33± 0.15 5.53± 0.05 5.36± 0.320.57 5.53± 1.25 Free- CO(mgl-1) 4±1 4.33± 1.52 4.66±1.15 4.33± 1.52 5.33±0.57 4.33±0.57 5±1 3.66±0.50 4.33± 0.57 4.66± 1.57 pH 6.93± 0.37 7.41± 0.13 6.69± 0.53 6.28± 0.17 6.43±0.20 6.64±0.11 7.86± 0.06 6.39± 2.08 6.04± 0.30 6.32± 0.035 Total alkalinity (mgl-1)19±10.1 18.66± 0.57 16±1 16.33± 0.57 28±1 20.6±2.51 23±1 18.33± 4.34 20±1 25.33± 1.52 Electrical conductivity (mS/cm) 0.0508±15.9 0.10743±2.90 0.1064±6.92 0.06066±0.30 0.0482±1.92 0.08823±40.95 0.0799±5.99 0.07593±4.34 0.0629±1.51 0.05246±2.65 Nitrate (mgl-1)2.61± 0.13 2.52± 0.40 0.32± 0.06 0.011± 0.011 1.006± 0.28 0.62±0.36 0.89±0.07 0.46± 0.03 0.537± 0.05 0.62± 0.04 Phosphate (mgl-1)0.095± 0.009 0.394± 0.05 0.39± 0.01 0.005± 0.005 0.33±0.019 0.02±0.02 0.42± 0.05 0.39± 0.03 0.091± 0.02 0.35± 0.03 The range of DO at pond 1 was 0.15mg l-1 to 0.86mg l-1 and pond 2 was 4.75mg l-1to 6.08mgl-1. Verylow DO concentration at pond 1 could be due to very low penetration of sunlight due to disposal of waste and growth of Lemna sp. which covered the pond. This facilitated more amount of organic matter decomposition instead of photosynthesis. Again the remaining amount of oxygen dissolved in water might have been utilized by the macrophytes. At pond 2 range of concentration of DO was relatively high. Range of F-CO of pond 1 (7.33mg l-1 to 22.66mg l-1) was much higher than pond 2 (3.66mg l-1 to 4.66mg l-1).A very high concentration of F-CO in water of pond1 could be due to higher respiration of aquatic biota, more decomposition of organic matter and low photosynthesis25. Phosphates ranged from 0.02 mg l-1 to 0.47 mg l-1 at pond 1 and 0.005 mg l-1 to 0.42 mg l-1 at pond 2.Phosphate concentration is generally low at Barak Valley as revealed in the previous study on nine different ponds28. The range of nitrates at pond 1 was 0.03mg l-1 to 0.499 mg l-1 and at pond 2 was 0.01mg l-1 to 2.61 mg l-1. However, at both the ponds the nitrates concentration was within the permissible limit of WHO29. In the industrial area of river Kapila, India, 2.6 mgl-1 of nitrate was recorded by Smitha30. Biomonitoring Scores: BMWP score ranged from 54 (pond 1, site 2) – 23 (pond 2, site 2) (table-8). Based on distribution and abundance of an individual family the BMWP Score values were computed to that family which again reflects their pollution tolerance. High BMWP scores mean pollution International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(8), 26-35, August (2014) Int. Res. J. Environment Sci. International Science Congress Association 34 intolerant families, while low scores mean pollution tolerant families18. The maximum value of BMWP score in pond 1, site 2 indicated relatively better water quality in that site. Table-8 shows the ASPT scores of the two ponds. Highest score was recorded at site 4 of pond 2 (5.75), whereas lowest score was recorded in site 1 of pond 1(4.78). A high ASPT usually characterizes clean sites. Disturbed sites generally have low ASPT values and do not support many high scoring taxa18.In SIGNAL score index, the macro-invertebrate families were computed by a ‘grade number’ between 1 and 10. The pollution tolerant families have a low grade number and sensitive to pollution families have a high number. Highest SIGNAL score was recorded in site 4 of pond 2 (4) whereas lowest score was recorded in site1of pond 1(2.25) (table-9). Table-8 BMWP and ASPT Scores of four sites of two ponds studied Ponds Sites BMWP scores No. of families ASPT scores Pond 1 Site 1 43 9 4.78 Site 2 54 11 4.9 Pond 2 Site 3 28 5 5.6 Site 4 23 4 5.75 N.B: BMWP score, 0-16=Poor water quality; 17-50=Moderate water quality; 51-100=Good water quality; 101-150=High water quality; 151+=Very high water quality (Source: Mandaville 2002). ASPT Value : �6= Clean water, 5-6= Doubtful quality, 4-5 = Probable moderate pollution, 4 = Probable severe pollution (Source: Mandaville 2002). Table-9 SIGNAL Score of the two ponds along with its water quality status Ponds Sites SIGNAL Score Water Quality status (Source: Gooderum and Tsyrlin 2002) Pond 1 Site 1 2.25 Severe pollution Site 2 2.28 Severe pollution Pond 2 Site 3 2.73 Severe pollution Site 4 4 Moderate pollution Conclusion Due to globalization and industrialization all the fresh water systems of urban areas are under threat. This study finds that even a small village converted to township is showing the sign of degradation of its fresh water systems.Hence there is a need for proper management. The authorities and management should come forward with protective measures to save the ponds from deterioration with the help of the municipalities, local peoples and NGOs. Acknowledgement The authors are thankful to the Head, department of Ecology and Environmental Science, Assam University, Silchar, India for providing laboratory facility and the owner of the fishery pond for giving permission to collect samples. 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