Phytoplankton Dynamics of Nigeen Lake in Kashmir Himalaya

International Journal of Environment and Bioenergy, 2013, 6(1): 13-27 International Journal of Environment and Bioenergy ISSN: 2165-8951 Journal homepage: www.ModernScientificPress.com/Journals/IJEE.aspx Florida, USA Article Phytoplankton Dynamics of Nigeen Lake in Kashmir Himalaya

Nuzhat Shafi *, Aftab Ahmad, Ashok K. Pandit

P.G. Department of Environmental Science, University of Kashmir, Srinagar-190 006, India

* Author to whom correspondence should be addressed; E-Mail: [email protected].

Article history: Received 3 March 2013, Received in revised form 27 March 2013, Accepted 29 March 2013, Published 4 April 2013.

Abstract: The present limnological study on Nigeen lake revealed that water of the lake was alkaline in nature and the total hardness was mainly due to bicarbonates of Ca2+ and Mg2+. Though the nutrient content of the lake was generally low, yet an increasing trend was noticed around floating gardens especially during summer. In total 30 genera of phytoplankton were identified, in which Chlorophyceae was the dominant class with 12 species, followed by Bacillariophyceae with 9 species, 7 belonged to Cyanophyceae and only 2 to Euglenophyceae. Phytoplankton exhibited its maximum growth and development during summer season near residential areas and floating gardens. A clear dominance of Chlorophyceae over Bacillariophyceae, Cyanophyceae and Euglenophyceae was observed throughout the study period. Shannon-Wiener index of phytoplankton signifies the water body to be moderately diverse as the values lies below 5.00 while as values of Simpson diversity index indicate accelerated eutrophication. However, Bray-Curtis cluster analysis showed the highest similarity between pollution rich sites while dissimilarity was observed between less polluted sites.

Keywords: alkaline; Chlorophyceae; Bacillariophyceae; floating gardens.

1. Introduction

In the vale of Kashmir, the fresh water lakes have a great ecological and economic importance. But unfortunately during last four decades, accelerated population growth and unplanned urbanization

Copyright © 2013 by Modern Scientific Press Company, Florida, USA Int. J. Environ. Bioener. 2013, 6(1): 13-27 14 have resulted in degradation of these lakes both in terms of their sprawl and water quality, thus adversely affecting the ecological functioning of these lakes. Phytoplanktons are important indicators for assessing the trophic status of lakes and act as bio- indicators of water quality (Wu and Suen, 1985). The role of phytoplankton in managing bio- energetics of lakes and their role as bio-indicators have been known for a long time (Kalyani and Charya, 1999). Eutrophic lakes support a large quantity of phytoplankton composed of few species, with a common and frequent pulses. Nigeen basin of Dal lake is a good example of such lakes which is undergoing racing eutrophication (Zutshi, 1980; Sarwar, Naqshi and Mir, 1996; Bhat and Pandit, 2002; Zutshi and Ticku, 2006; Salum and Wanganeo, 2008). The aim of present study is to provide current trophic status of the lake on the basis of phytoplankton community structure and physico-chemical analysis of water.

2. Study Area

For the present study four sampling sites of Nigeen lake were selected on the basis of water depth, vegetation, biotic variables and anthropogenic stresses (Figs 1 & 2). The first site with depth of 1.5-2.5 m was located in south west area of lake near residential area known as Khuj yarbal. The second site with 4.0 m deep being located in central area of the lake was clear with patchy growth of macrophytic vegetation. The third site was located near Golf club associated with house boats and its depth ranged from 2.0-2.6 m. The water of this site was slightly turbid compared to first site with sparse growth of macrophytic vegetation. The fourth site was located in the north east side of Hazratbal basin near Ashaibagh bridge acting as inlet source of Nigeen basin and receiving water from other basins of Dal lake. The depth at this site ranged from 2.3-2.7 m.

3. Material and Methods

The sampling was carried out on monthly basis from July to December in 2008. Five liters of water collected at a depth of approximately 0.5 m were sieved through plankton net of bolting silk (mesh Size No. 25 mm). Plankton samples were collected and preserved in 5 mL of Lugol’s iodine solution. After keeping it for 24 h, the supernatant was discarded and 20 mL concentrated sample was obtained. Quantitative estimation of phytoplankton was done under microscope, with the help of Sedgwick rafter counting cell of 1 mL capacity. A single colony in case of colonial forms, a single filament in case of filamentous forms and a single organism has been referred to as a unit (Welch, 1948). Identification of the phytoplankton was done with the help of standard works of Edmondson (1992) and Hutchinson (1967). Among physico-chemical parameters besides DO fixation, depth and temperature (air and

Copyright © 2013 by Modern Scientific Press Company, Florida, USA Int. J. Environ. Bioener. 2013, 6(1): 13-27 15 water) were measured on the spot while remaining parameters of water were determined in the laboratory within 24 h of the sampling following the standard methods (Golterman et al., 1978; APHA, 2004).

Figure 1. Outline of Nigeen lake Figure 2. Sampling sites in Nigeen lake

4. Results and Discussion

4.1. Physico-Chemical Characteristics of Water

Table 1. Physico-chemical characteristics of water (Mean  SD) at four different sites of Nigeen lake (July-December 2008) Parameter Site I Site II Site III Site IV Temp. Air (°C) 22.66 ± 6.91 22.83 ± 7.27 22.33 ± 7.08 23.16 ± 7.08 Temp. Water (°C) 19.66 ± 6.7 19.16 ± 8.1 18 ± 7.3 19.5 ± 7.8 Depth (m) 2.40 ± 0.0 2.57 ± 0.0 2.9 ± 0.5 2.52 ± 0.0 pH 7.9 ± 0.6 8.21 ± 0.2 8.43 ± 0.4 8.27 ± 0.2 D.O (mg/L) 5.45 ± 0.7 7.26 ± 1.1 7.66 ± 0.8 7.23 ± 1.4 Chloride (mg/L) 27.14 ± 7.7 19.85 ± 7.8 29.73 ± 3.5 22.58 ± 7.5 Ca hardness (mg/L) 32.13 ± 11.4 33.36 ± 10.7 33.9 ± 10.4 38.36 ± 10.2 Mg hardness (mg/L) 6.86 ± 1.9 15.71 ± 2.5 11.58 ± 4.2 15.91 ± 2.6 Total hardness (mg/L) 43.33 ±14.1 50.25 ± 12.1 46.31 ± 14.3 54.28 ± 10.9

Alkalinity CO3 (mg/L) Absent 2.96 ± 2.11 2.64 ± 2.36 2.9 ± 1.76

Alkalinity HCO3 (mg/L) 74.88 ± 2.7 71.33 ± 18.0 56.28 ± 17.9 58.74 ± 6.1 Total alkalinity (mg/L) 74.88 ± 2.7 74.3 ± 17.4 58.48 ± 18.4 69.43 ± 5.8

Ortho- PO4 (µg/L) 338.33 ± 53.0 270 ± 38.9 199.5 ± 29.0 257.33 ± 53.0

4.1.1. Temperature Temperature is the most important factor regulating the growth and dynamics of phytoplankton and effects indirectly on different biological communities in regulating competition and variation (Vera Lucia et al., 2008). During the entire study period surface water temperature ranged from a minimum of 8 °C at site III in December to a maximum of 27 °C at site II in July and followed closely to air temperature which ranged from a minimum of 13 °C at site II in December to 30 °C in July at site II.

4.1.2. Depth Water depth varied from a minimum of 2.31 m at site I in September to a maximum of 3.90 m at site III in October. It may be possibly due to sedimentation, eutrophication and dredging which was found to alter the depth of lake. Wanganeo (1984) reported that lakes of Kashmir valley are usually shallow with the mean depth for all ranging from 0.6 to 3.0 m and the maximum from 5.8 to 13 m.

4.1.3. pH The pH is the negative logarithmic expression of hydrogen ion concentration and also acid- alkalinity deciding factor. During the entire study period pH was found to be alkaline in nature ranging from a minimum of 7.2 at site I in November to a maximum of 8.9 at site I in August. An increasing trend was observed during summer. The lake water seemed to be well buffered as no abrupt changes were observed in the pH value.

4.1.4. Dissolved oxygen Dissolved oxygen is one of the most important abiotic factors influencing an aquatic environment. It plays a significant role in the regulation of metabolic processes of communities and organisms and also as an indicator of the lake condition (Reid, 1961). Its concentration in natural waters depends upon many factors viz. temperature, decompositional activities, photosynthesis and the level of aeration (Zutshi and Vass, 1978). The dissolved oxygen content of the lake ranged from a minimum of 4.4 mg/L in August at site I to a maximum of 9.1 mg/L in October at site III. Its values were low during summer and increased towards winter months which are significant with change in environmental conditions like temperature.

4.1.5. Chloride Chloride content ranged from a minimum of 14 mg/L in November at site II to a maximum of 36 mg/L in October at site IV. Floating gardens along with domestic wastes from houseboats and dense urban population around the Nigeen lake seems to be the cause of high chloride content. Siraj

Copyright © 2013 by Modern Scientific Press Company, Florida, USA Int. J. Environ. Bioener. 2013, 6(1): 13-27 17 and Yousuf (2002) have also found that the water near floating gardens was more enriched with nutrients like phosphorus, nitrogen and chloride, which lead to high growth of algal and macrophytic vegetation with common pulses.

4.1.6. Total hardness Total hardness ranged from a minimum of 30.4 mg/L at site I in July to a maximum of 70.2 mg/L at site II in October. Calcium was recorded to be the most dominant cation in the lake. The values of calcium fluctuated from a minimum of 19 mg/L at site IV in July to a maximum of 55.3 mg/L at site I in October. Magnesium fluctuated from a minimum of 4.2 mg/L in August at site III to a maximum of 18 mg/L in December at site III. Magnesium content in the lake water generally remained low, possibly due to uptake of Mg2+ by macrophytes and phytoplankton for the formation of chlorophyll and enzymes. Zutshi et al. (1980) have reported a ratio of 3:1 for calcium and magnesium in Kashmir lakes. The predominance of calcium in Nigeen lake seems to be due to the presence of lime rich rock strata as also due to the use of lime and superphosphate fertilizers in floating gardens.

4.1.7. Alkalinity Alkalinity was of bicarbonate type and varied from a minimum of 35.0 mg/L in July at site III to a maximum of 84.0 mg/L in December at site II. Rawson (1956) reported that the phytoplankton species grow best in quite alkaline water and use the bicarbonate ion as a carbon source in photosynthesis.

4.1.8. Ortho-phosphorus (PO4) During the entire study period ortho-phosphorus concentration ranged from a minimum of 160 µg/L in December at site I to a maximum of 400 µg/L in August at site I thereby, depicting contamination by domestic and agricultural wastes, originating mainly from the Srinagar city thus, posing serious threat to the biological diversity of the lake. Hutchinson (1967) stated that the quantity of phytoplankton in any water is more likely determined by concentration of combined nitrogen and phosphorus than by any other factor

4.2. Phytoplankton Dynamics

4.2.1. Species composition In all a total of 30 genera of phytoplankton were counted in Nigeen lake in which class Chlorophyceae was dominant, registering the highest of 12 taxa (Chlorella, Cosmerium, Closterium, Sphaerocystis, Selanastrum, Tetradon, Coelastrum, Cosmerium, Closterium and Desmidium) followed

Copyright © 2013 by Modern Scientific Press Company, Florida, USA Int. J. Environ. Bioener. 2013, 6(1): 13-27 18 by Bacillariophyceae with 9 taxa (Amphora, Cymbella, Diatoma, Eunotia, Fragilaria, Navicula and Synedra) while, Cyanophyceae was represented by 7 taxa (Chrococcus, Lyngbya, Nostoc, Oscillatoria, Spirulina, Rivularia and Microcystis) and Euglenophyceae registered only 2 taxa (Euglena and Phacus). The most abundant species in genera Chlorophyceae was Chlorella while Sphaerocystis and Selanastrum were least abundant. Similarly in class Bacillariophyceae Fragilaria was most abundant and Diatoma was least abundant. Among Cyanophyceae the most abundant species was Oscillatoria and the least abundant species was Rivularia. In Euglenophyceae, the most abundant species was Phacus and the least abundant species was Euglena.

4.2.2. Population density During the entire study period Chlorophyceae was most dominant class in terms of density followed by Bacillariophyceae, Cyanophyceae and Euglenophyceae (Fig. 3). At Site I the proportion of Chlorophyceae was 55.7%, Bacillariophyceae contributed 20.0%, Cyanophyceae (18.53%) and Euglenophyceae (5.6%). The percentage composition of Chlorophyceae at Site II was considerably higher (52.5%), than all other sites and same was true for Bacillariophyceae (19.9%), Cyanophyceae (22.9%) and Euglenophyceae (4.6%). At Site III the percentage composition of Chlorophyceae was 53.0%, followed by Bacillariophyceae with 20.87%, Cyanophyceae was 21.5% and Euglenophyceae was 4.5%. At Site IV Chlorophyceae made 55.1% of density followed by Bacillariophyceae (20.5%) Cyanophyceae (19.52%) and Euglenophyceae (4.78%) (Fig. 4).

Figure 3. Overall percentage contribution of different classes during whole study period

Figure 4. Percentage contribution of each class at different sites

The occurrence and abundance of phytoplankton showed a close relationship with the changes in the physico-chemical characteristics of water (Kaul et al, 1978; Pandit, 1980; Ganai et al., 2010). The pollution tolerant taxa like Cymbella and Oscillatoria were sparse at sites II, III and IV except at Site I where it was most abundant in nutrient enriched waters due to presence of large floating gardens and nearby residential area (Findlay et al., 1994) (Tables 2-5). This finding gains further support from the studies of Hutchinson (1967) who opined that increase in concentration of phosphorus and nitrogen has direct impact on the primary productivity and the development of phytoplankton community. The phytoplankton community in the Nigeen lake was dominated by Chlorophyceae followed by Bacillariophyceae, Cyanophyceae, and Euglenophyceae. Such a type of algal composition and the presence of some oligotrophic species (Diatoma sp., Eunotia sp.) signifies a transitional trophic level of lake as opined by Rawson (1956) according to whom the algal groups of oligotrophic lakes are mainly Chlorophyceaen forms, which might also be accompanied by Diatomaceae and Chrysophyceae.

Table 2. Monthly variation in population of phytoplankton at site I during July - December 2008 in Nigeen lake Chlorophyceae Jul. Aug. Sept. Oct. Nov. Dec. Total Mean Chlorococales Chlorella sp. 600 560 450 300 100 45 2055 342.5 Coelastrum sp. 480 250 140 120 70 30 1090 181.7 Pediastrum sp. 400 280 150 100 30 20 980 163.3 Sphaerocystis sp. 100 60 50 55 25 5 295 49.2 Scenedesmus sp. 500 410 380 250 100 30 1670 278.3 Selanastrum sp. 180 170 140 80 60 10 640 106.6 Tetradon sp. 300 250 200 100 80 20 950 158.3 Desmidaceae

Desmidium sp. 250 180 80 30 10 5 555 92.5 Cosmerium sp. 200 160 90 60 30 - 540 90.0 Closterium sp. 300 220 120 100 60 - 800 133.3 Bacillariophyceae Amphora sp. 150 140 80 60 40 5 475 79.2 Cymbella sp. 200 170 80 60 20 5 535 89.2 Diatoma sp. 110 90 85 30 30 5 350 58.3 Eunotia sp. 60 30 25 30 30 10 185 30.8 Fragilaria sp. 260 280 195 77 60 40 912 152.0 Navicula sp. 150 120 85 40 20 5 420 70.0 Synedra sp. 200 140 90 75 30 20 555 92.5 Cyanophyceae Chrococcus sp. 140 110 70 30 20 5 375 62.5 Lyngbya sp. 160 120 80 25 20 10 415 69.16 Nostoc sp. 120 90 60 40 20 10 340 56.6 Oscillatoria sp. 220 180 80 40 40 20 580 96.66 Rivularia sp. 130 105 70 60 20 5 390 65 Microcystis sp. 215 135 90 70 50 20 580 96.66 Spirulina sp. 190 150 80 50 25 5 500 83.33 Euglenophyceae Euglena sp. 125 100 80 60 40 5 410 68.33 Phacus sp. 125 110 190 80 50 8 563 93.83

Table 3. Monthly variation in population of phytoplankton at site II during July - December 2008 in Nigeen lake Chlorophyceae Jul. Aug. Sept. Oct. Nov. Dec. Total Mean Chlorococales Chlorella sp. 130 100 80 60 30 10 410 68.3 Coelastrum sp. 120 90 85 80 10 20 405 67.5 Pediastrum sp. 200 170 150 80 40 10 650 108.3 Scenedesmus sp. 180 80 70 40 45 10 425 70.8 Sphaerocystis sp. 80 50 30 20 - - 180 30.0 Selanastrum sp. 190 160 110 75 30 - 565 94.2 Tetradon sp. 220 160 120 80 40 20 640 106.6 Desmidaceae Desmidium sp. 100 50 35 9 - - 194 32.3 Cosmerium sp. 100 40 20 10 - - 170 28.3 Closterium sp. 150 70 80 30 - - 330 55.0 Bacillariophyceae Amphora sp. 120 70 50 20 5 - 265 44.2

Cymbella sp. 100 70 30 10 - - 210 35.0 Diatoma sp. 80 50 20 10 5 - 165 27.5 Eunotia sp. 30 25 25 15 5 - 100 16.6 Fragilaria sp. 120 75 40 30 15 5 165 27.5 Navicula sp. 95 80 30 15 10 - 230 38.3 Synedra sp. 100 70 45 20 10 5 250 41.6 Cyanophyceae Chrococcus sp. 140 100 50 10 10 - 310 51.6 Lyngbya sp. 100 70 60 30 15 5 280 46.6 Nostoc sp. 80 60 55 30 5 - 230 38.3 Oscillatoria sp. 80 50 20 15 10 5 180 30.0 Rivularia sp. 60 40 35 20 10 - 165 27.5 Microcystis sp. 120 98 60 40 10 5 333 55.5 Spirulina sp. 100 80 40 5 10 5 240 40.0 Euglenophyceae Euglena sp. 70 50 30 20 10 - 180 30.0 Phacus sp. 80 40 25 13 10 - 168 28.0

Table 4. Monthly variation in population of phytoplankton at site III during July - December 2008 in Nigeen lake Chlorophyceae Jul. Aug. Sept. Oct. Nov. Dec. Total Mean Chlorococales Chlorella sp. 300 250 160 100 80 15 905 150.83 Coelastrum sp. 110 100 80 60 20 5 375 62.5 Pediastrum sp. 500 480 260 130 80 30 1480 246.6 Scenedesmus sp. 450 380 250 120 20 - 1220 203.3 Sphaerocystis sp. 120 60 50 30 5 - 265 44.16 Selanastrum sp. 110 65 50 45 25 10 305 50.83 Tetradon sp. 230 200 120 80 30 5 665 110.83 Desmidaceae Desmidium sp. 180 90 70 30 - - 370 61.6 Cosmerium sp. 140 100 90 50 20 - 400 66.6 Closterium sp. 210 100 100 60 20 - 490 81.6 Bacillariophyceae Amphora sp. 180 120 90 85 30 10 515 85.8 Cymbella sp. 110 115 80 65 25 5 400 66.6 Diatoma sp. 110 90 50 30 20 10 310 51.6 Eunotia sp. 90 70 35 25 10 5 235 39.16 Fragilaria sp. 100 80 65 50 30 15 340 56.6 Navicula sp. 150 90 70 30 10 - 350 58.33

Synedra sp. 130 100 85 55 25 5 400 66.6 Cyanophyceae Chrococcus sp. 300 210 200 140 20 5 875 145.8 Lyngbya sp. 80 60 50 30 5 5 230 38.33 Nostoc sp. 80 60 50 45 20 - 255 42.5 Oscillatoria sp. 110 70 60 30 10 5 285 47.5 Rivularia sp. 100 60 55 40 10 - 265 44.16 Microcystis sp. 110 80 10 20 5 - 225 37.5 Spirulina sp. 180 130 100 70 20 - 500 83.33 Euglenophyceae Euglena sp. 80 70 55 40 10 5 300 50 Phacus sp. 130 80 40 30 15 - 255 42.5

Table 5. Monthly variation in population of phytoplankton at site IV during July - December 2008 in Nigeen lake Chlorophyceae Jul. Aug. Sept. Oct. Nov. Dec. Total Mean Chlorococales Chlorella sp. 550 400 285 210 110 80 1630 271.7 Coelastrum sp. 180 150 160 100 50 30 675 112.5 Pediastrum sp. 180 150 100 40 20 - 490 81.6 Scenedesmus sp. 380 360 220 190 110 30 1290 215.0 Sphaerocystis sp. 150 80 60 30 5 5 330 55.0 Selanastrum sp. 110 80 65 55 30 20 360 60.0 Tetradon sp. 260 250 210 150 80 20 970 161.6 Desmidaceae Desmidium sp. 200 120 60 25 - - 405 67.5 Cosmerium sp. 130 80 60 30 - - 300 50.0 Closterium sp. 210 110 90 50 10 - 470 78.3 Bacillariophyceae Amphora sp. 100 80 30 10 5 - 225 37.5 Cymbella sp. 200 180 100 60 20 5 565 94.2 Diatoma sp. 180 120 80 60 20 5 465 77.5 Eunotia sp. 40 20 20 15 10 - 105 17.5 Fragilaria sp. 260 120 80 70 50 30 610 101.6 Navicula sp. 120 70 70 30 10 - 300 50.0 Synedra sp. 130 80 50 30 15 5 310 51.6 Cyanophyceae Chrococcus sp. 150 120 80 20 10 - 380 63.3 Lyngbya sp. 130 115 70 60 20 5 400 66.6 Nostoc sp. 100 60 30 - 20 5 395 65.8

Oscillatoria sp. 150 100 70 50 20 5 395 65.8 Rivularia sp. 120 70 65 30 10 - 295 49.2 Microcystis sp. 90 60 30 20 10 - 210 35.0 Spirulina sp. 100 110 90 50 30 10 390 65.0 Euglenophyceae Euglena sp. 120 110 80 60 20 5 395 65.8 Phacus sp. 150 90 60 40 30 5 375 62.5

4.3. Phytoplankton Diversity Indices

In the present investigation, dominance index showed site II (0.048) the least dominant in algal forms and site IV (0.056) as most dominant possibly due to presence of floating gardens and flow of water from other basins of lake which may increase nutrient load and indirectly density of phytoplankton at site IV. Shannon-Wiener diversity index ranged from 3.084 to 3.142 during entire study. The highest Shannon-Wiener diversity index (3.142) was noticed at site II and the lowest (3.084) was observed at site IV. In general high value of Shannon-Wiener index signifies that among all studied sites, site II is highly diverse and also supports the fact that the water body is moderately diverse as the value lies below 5.00. In Shannon-Wiener index, a water body is classified as: very good when H´ is > 4, good quality 4-3, moderate quality 3-2, poor quality 2-1 and very poor quality <1. Rao (1984) also reported relatively low index value (1.58 - 2.90) for a eutrophic lake of Udaipur. Wilhm and Dorris (1968) found that the value of index declined sharply in polluted zones of the lake. The value of Simpson index ranges between 0 and 1. The greater the value is, the greater the sample diversity is. Simpson diversity index varied from 0.944 to 0.952 in the present study which means that value is approaching 1, signifying that lake has high relative diversity. However the minimum value of 0.944 was recorded at site IV and a maximum of 0.952 was maintained at site II. A scale of pollution in terms of Simpson species diversity (3.0 - 4.5 slight, 2.0 - 3.0 light, 1.0 - 2.0 moderate and 0.0 - 1.0 heavy pollution) has been described by Staub et al. (1970). The values of Simpson diversity index in the present water body indicate heavy pollution (Table 6). The evenness diversity index ranged from 0.840 at site IV to 0.891 at site II. The minimum trend of variation in evenness values indicated site II is slightly diverse among all other sites. This data support the theory that the dominance index is opposite to the evenness index (Patrick and Charles, 1967). Overall diversity of study sites also got repeated by diversity profile graph in which site II deputed the highest diversity and site IV represented the least diversity (Fig. 5). The results of the Bray-Curtis cluster analysis showed that the highest similarity on the basis of phytoplankton was observed between sites III and IV while extreme differences in the phytoplankton structure was

Copyright © 2013 by Modern Scientific Press Company, Florida, USA Int. J. Environ. Bioener. 2013, 6(1): 13-27 24 detected with respect to site II (Fig. 6). Overall percentage contribution of each class during whole study period was Chlorophyceae with 55%, Bacillariophyceae with 20%, Cyanophyceae with 20% and Euglenophyceae with 5% (Fig. 3).

Table 6. Diversity indices of study sites I II III IV Taxa (S) 26 26 26 26 Individuals (I) 17160 7440 12215 12735 Dominance (D) 0.054 0.048 0.055 0.056 Shannon Wiener (H) 3.099 3.142 3.086 3.084 Simpson (1-D) 0.946 0.952 0.945 0.944 Evenness_(H/S) 0.853 0.891 0.842 0.840

I IV II III

Diversity 18

10 0 0.5 1 1.5 2 2.5 3 3.5 alpha Figure 5. Diversity profiles of different study sites

0.64

0.68

0.72

0.76

0.84

0.88 0.92

Similarity 0.96

0.8

0.5 1

III

1.5

Bray-Curtis clustering Bray-Curtis 2

2.5 3

3.5 4

II 4.5

Figure 6. Cluster analysis of study sites

5. Conclusions

Above results bring light to the fact that Nigeen lake, an important ecosystem both from the ecological and economic point of view is under constantly increasing anthropogenic pressure resulting in encroachment, pollution of water, weed infection, siltation etc. and if the present trend of excessive anthropogenic pressure and resultant degradation of lake is not addressed in time the lake may degrade beyond retrieval and must face an ecological disaster. The value of Shannon-Wiener index, Simpson index, evenness, Bray-Curtis cluster signifies that lake has high relative diversity with moderate pollution. Therefore an integrated and multidisciplinary approach is needed to conserve this lake from further degradation.

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