Spatio-temporal variations in the community structure of macrobenthic invertebrate fauna of Gharana Wetland (reserve), Jammu (J&K, India).
Wetlands are among the most productive ecosystems of the world with specific ecological characteristics, functions and values. They are essential life- supporting systems providing a wide array of benefits to human kind. Their high productivity places them among the richest and most biologically diverse ecosystems in the world (Kivaisi, 2001; Samsunlu et al, 2002)[1,2]. The importance of wetland habitats for human society and as a store of biological diversity has become increasingly recognized on a global scale since the late 1960s (Cowan, 1995; Ramsar COP8, 2002). Most of the wetlands in India are host to rare, threatened and endangered species of flora and fauna (Menon, 2004). Macrobenthos are greater than 0.5 mm size, exhibit variety of body shapes, feeding styles, reproductive modes and perform varieties of ecological functions. They act as a connecting link between the biotopes of substratum and water column in the aquatic systems. They take part in breakdown of particulate organic material and export energy to higher trophic level and can potentially support offshore and pelagic communities (Schrijvers et al, 1996; Lee, 1997)[6,7]. The developmental stages of many macrobenthic organisms are pelagic, forming important components of plankton community, that in turn is consumed by fish and thus having high influence on pelagic fisheries. Thus, the estimation of benthic production is useful to assess the fishery production of a particular area (Sultan Ali et al, 1983). Benthic invertebrate are particularly favored because they are relatively sedentary and therefore representative of local conditions (Cook, 1976) . Thus, in freshwater ecosystems, macro invertebrate indicator taxa are widely used to assess the quality and pollution status of a water body (Reynoldson, 1984) . The present study has been undertaken to determine the community structure, density and other ecological characteristics of macrobenthic fauna in relation to physico- chemical parameters of the wetland so that this piece of information could be utilized to evaluate the present status of the wetland.
Gharana Wetland (Reserve) 32[degrees] 32' 26" N, 74[degrees] 41' 24" E is situated in Jammu and Kashmir State, Northwestern India (~) 10 miles east of the Indo-Pakistan International border (Fig.1). Gharana Wetland is under J&K Wildlife Protection Act, 1978 and is declared as 'Important Bird Area'. This wetland lies along the Palaearctic - Oriental migratory route of aquatic birds and thus, besides being the habitat of different biota, this wetland serves as a wintering ground for many species of the birds. During the period of present study (March, 2008 to February, 2009), Gharana Wetland (Reserve) was divided into four stations:
Station I: This station lies close to Gharana village and is under continuous stress of anthropogenic influences. Cattle-bathing, washing of vehicles and disposal of cowdung along with other house-hold waste materials are the common activities occurring at this station.
Station II: It is about 300 m away from St I. Despite being very close to Gharana village, this station is not under much anthropogenic stress as compared to Station I.
Station III: It is situated exactly opposite to St I and is about 600 m away from St II.
It is bordered by large agricultural fields and thus receives agricultural run- off from these fields.
Station IV: It is about 530 m away from St I and is situated on the road side. This station receives a spill over water from Ranbir Canal.
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Material and Methods
Sampling: Macro-benthic invertebrate samples were collected monthly by using Ekmann's dredge from the preselected stations. Four bottom samples were taken from each station to minimize the sampling error. Samples collected were then sieved through sieve no. 40 having 256 meshes per sq. cm (Edmondson and Winberg, 1971)  and packed in labeled polythene bags. Samples were washed in the laboratory; organisms were sorted and then preserved in 5% formalin or 90% ethylalcohol for further identification.
Qualitative analysis: The qualitative analysis of preserved samples of macro- benthic invertebrate fauna was done by following Ward and Whipple (1959), Needham and Needham (1962), Macan (1964), Tonapi (1980), Adoni (1985) and Pennak (1989).
Quantitative analysis: Preserved samples of macro-benthic invertebrate fauna were subjected to quantitative analysis applying the formula: n = O/(a.s ) (10,000), where n is the number of macro-benthic invertebrates per meter square, O is the number of organisms counted, a is the area of metallic sampler in square meter and s is the number of samples taken at each station (Welch, 1948) .
All the physico-chemical characteristics of water were determined at the sampling sites. The water and air temperature was recorded by a mercury bulb thermometer, depth by a meter rod and transparency by secchi disc. pH of the water was determined by using a portable pH meter (Hanna, model HI 98130). Dissolved oxygen of the water was estimated by sodium azide modification of Winkler's method, FCO2 by Titrimetric method, chlorides by Argentometeric method (A.P.H.A., 1985) . Carbonates and bicarbonates were determined as per I. S. I. Method (1973), A.P.H.A. (1985) and Adoni (1985).
Standard Deviation (sd) was calculated using the formula: SD = [square root of ([summation][d.sup.2]/n)], where d is the deviation from the mean (x - [x.sup.-]) and n is the total number of observations. Species diversity was determined by applying Shannon-Weaver Diversity Index (Shannon and Weaver 1949), H' = -[[summation].sup.s.sub.i=1][p.sub.i].ln([p.sub.i]), in which H' is the information content of sample (bits/individuals), S is the number of species and [p.sub.i] is the proportion of total species belonging to ith species. Simpson's Index of dominance (C) was calculated according to Stone and Pence (1978), C = [[summation].sup.s.sub.i=1][p.sub.i.sup.2] where [p.sub.i] is the proportion of total number of individuals of each species. Species richness was determined applying Marglefs Index (Marglef, 1968), d' = S - 1/[Log.sub.n] (N), in which S is the total number of species, N is the total number of individuals in sample and [Log.sub.n] is the Natural log. Evenness was calculated using the Pielou's Index, E = H'/ln S (Pielou, 1969), where H' is the Index of diversity of Shannon-Weaver, ln is the Natural log and S is the total number of species.
Scattergrams, resulting from plotting changes in overall macrobenthic abundance (dependent variable) against corresponding changes in the physico-chemical factors (independent variables), and the fitted regression lines (y = a + bx) were computed to predict any change in the quantitative relationship between the dependent and independent variables (Chattopadhyay and Banerjee, 2007). Percentage similarity of the macrobenthic invertebrate communities in different seasons was calculated by Sorenson's Quotient of Similarity (Sorenson, 1948), Q/S = 2j/a + b (100), where j is the number of species common to both samples, a is the total number of species in sample 1 and b is the total number of species in sample 2. Morisita-Horn Index (Wolda, 1983) was applied to determine the similarity of macrobenthic communities in different seasons in terms of abundance using the formula: MH = 2 [[summation].sup.n.sub.i=1] ([N.sub.ia] [N.sub.ib])/([d.sub.a] + [d.sub.b]) [N.sub.a][N.sub.b], in which [N.sub.ia] & [N.sub.ib] number of individuals of species 'i' in the samples for site a and b, [N.sub.a] & [N.sub.b] are the number of individuals in the samples from sites a and b and n is the total number of species.
Diversity indices were correlated using Karl Pearson's Coefficient of Correlation which was tested at 5% level using Student-t test. Two-way ANOVA was used to determine whether there is significant temporal variations in the different characteristics of macrobenthic community among different seasons/months as well as stations. Correlation Coefficient, Student-t test and Two-way ANOVA was calculated with the help of Microsoft Excel (MS Office, 2007) and SPSS Software (Ver. 16.0).
The physico-chemical variables for Gharana Wetland are presented in Table 1. The range of air and water temperature throughout the study period varied from 14 to 39 0C and 13 to 35 0C respectively. The range of depth and transparency varied from 6.5 to 85 cm and 1.5 to 58.5 cm respectively, the lowest being during the premonsoon and highest during monsoon period. pH varied widely from 6.6 to 9.6 but it indicated an alkaline condition during most of the study period. Concentration of Dissolved Oxygen was observed to fluctuate from 1.6 to 8.4 mg/l and of free carbon dioxide from 0-40 mg/l. Carbonates were found absent during most of the months. Higher concentration of bicarbonates was observed during late winters and spring. Calcium concentration ranged from 16.04 to 64.16 mg/l. Chloride (518.96 mg/l) and magnesium (94.77 mg/l) displayed its highest values at St I.
Present investigations on macrobenthic invertebrate fauna of Gharana Wetland (Reserve) revealed the presence of three major Phyla- Annelida, Arthropoda, and Mollusca. A total of 39 species of macrobenthic invertebrates were identified, 5 species of Phylum Annelida, 30 species of Arthropoda and 4 species of Mollusca (Table 2). Arthropoda dominated the macrobenthic community (77.72%) whereas remaining phyla exhibited the lower percentages viz. Annelida (13.73%) and Mollusca (8.55%) (Fig. 3). Maximum species (34) were found at St I followed by 29 species at St IV, 28 species at St III and a minimum of 25 species at St II.
[FIGURE 3 OMITTED]
Phylum Annelida was represented by two classes- Class Oligochaeta (3 species) and Hirudinea (2 species). Of all the annelid taxa, Helobdella sp. Blanchard was exclusively recorded at St III while Hirudinaria granulosa (Savigny) was completely absent at St I. Class Insecta, the only contributor to Phylum Arthropoda, was comprised of 5 orders namely Coleoptera (12 species), Diptera (8 species), Hemiptera (7 species), Odonata (2 species) and Ephemeroptera (1 species). Among arthropods, only 14 species were abundant and ubiquitous including Sphaerodema annulatum Fabricius, Sphaerodema molestum Duf., Laccotrephes maculates (Fabricius), Corixa hieroglyphica Duf., Notonecta sp. Linne, Regimbartia attenuata (Fabricius), Berosus pulchellus Mackleay, Hydrovatus acuminatus Motschulsky, Hypophorus sp. Sharp, Laccophilus flexusus (Aube), Canthydrus laetibilis (Walker), Paedrus extraneus Wied., Chironomus sp. Meigen and Culicoides sp. Latreille. Phylum Mollusca was represented by Class Gastropoda which comprised of 4 species. These species belonged to 3 families: Planorbidae, Lymnaedae and Viviparidae. Only Gyraulus sp. inhabited all the stations (Table 2).
The standing crop of total macrobenthic population throughout the study period was highest at St I (19287 ind.[m.sup.-2]) followed by St II (6345 ind.[m.sup.-2]), St IV (4725 ind.[m.sup.-2]) and St III (4059 ind.[m.sup.-2]). A well marked seasonal variation in total macrobenthic invertebrate fauna existed that ranged from 9-6489 ind.[m.sup.-2] at St I, 81- 2151 ind.[m.sup.-2] at St II, 54-477 ind.[m.sup.-2] at St III and 126-675 ind.[m.sup.-2] at St IV. Macrobenthic fauna acquired their peak in the month of September at St I (6489 ind.[m.sup.-2]), St II (2151 ind.[m.sup.-2]) and IV (675 ind.[m.sup.-2]) while during April at St III (603 ind.[m.sup.-2]) (Fig. 2a). On the other hand, minimum density was recorded in May at all the stations. Comparative account of annual percent contribution of annelids to macrobenthic density at different stations revealed that annelids contributed 9.52%, 17.73%, 23.28% and 17.33% at St I, II, III and IV respectively (Fig. 3). Comparison between stations showed the highest density of annelids (153 ind.[m.sup.2] [+ or -] 364.60) at St I, thus contrasting with the lowest density (68.25 ind.[m.sup.-2] [+ or -] 86.60) at St IV. ST II and III had the density of 93.75 ind.[m.sup.-2] [+ or -] 241.45 and 78.75 ind.[m.sup.-2] [+ or -] 102.49 respectively. Maximum annelid population was recorded in September at St I (1350 ind.[m.sup.- 2]) and St II (891 ind.[m.sup.-2]) while during April at St III (288 ind.[m.sup.-2]) and St IV (261 ind.[m.sup.-2]). Complete absence of annelids was observed during March, May and October to November at St III. At St IV, annelids were found to be absent from May-August (Fig. 2b).
Maximum annelid density at all the stations was mainly contributed by Class Oligochaeta. The density of Oligochaetes was observed to be highest at St I (153 ind.[m.sup.-2] [+ or -] 364.60). Among Oligochaetes, the participation of Tubifex tubifex was shown to be maximum at all the stations with highest mean standing crop at St I (136.5 ind.[m.sup.-2] [+ or -] 369.36) followed by St II (84 ind.[m.sup.-2] [+ or -] 241.42), St III (67.5 ind.[m.sup.-2] [+ or -] 98.97) and St IV (60.75 ind.[m.sup.-2] [+ or -] 84.12).
Arthropods contributed 86.00%, 76.88%, 59.87% and 60.38% (Fig. 3) to the total arthropod density with mean standing crop of 1382.25 ind.[m.sup.-2] [+ or -] 1752.79, 406.5 ind.[m.sup.-2] [+ or -] 357.34, 202.5 ind.[m.sup.-2] [+ or -] 131.12 and 237.75 ind.[m.sup.-2] [+ or -] 146.53 at St I, II, III and IV respectively. Maximum density of arthropods was observed during November at St I (5265 ind.[m.sup.-2]) and St IV (513 ind.[m.sup.-2]), during September at St II (1260 ind.[m.sup.-2]) and during December at St III (414 ind.[m.sup.-2]). Least arthropod count was recorded during May at St I (9 ind.[m.sup.-2]), August at St II (0 ind.[m.sup.-2]) and July at St III (36 ind.[m.sup.-2]) and St IV (27 ind.[m.sup.-2]) (Fig. 2c).
Figure 3 represented the relative abundance of various orders of arthropoda of four stations. During the present investigations, dipterans ranked first in their numerical abundance at St I (1079.25 ind.[m.sup.-2] [+ or -] 1534.65) and St II (264 ind.[m.sup.-2] [+ or -] 310.76). Dominance of Dipterans at these stations was owing to the greater density of Chironomus at St I (958.5 ind.[m.sup.-2] [+ or -] 1551.03) as well as at St II (229.5 ind.[m.sup.-2] [+ or -] 289.83). Conversely, Coleoptera occupied significant place in terms of their numerical abundance at St III (139.5 ind.[m.sup.-2] [+ or -] 126.51) and St IV (129 ind.[m.sup.-2] [+ or -] 118.79) thereby leading to the peak of total arthropod population during winter at these stations.
Ephemeroptera recorded their complete absence at St III and IV while comparatively more density of ephemeropterans at St I (4.5 ind.[m.sup.-2] [+ or -] 10.71) as compared to St II (2.25 ind.[m.sup.-2] [+ or -] 7.46) was observed. Among Hemiptera, Notonecta sp. and Corixa hieroglyphica donated maximum to the total hemipteran population at all the stations. Odonates were found to be absent at St II while their presence was recorded at rest of the stations in the monsoon period.
Molluscs weakly occurred at St I (4.48%), St II (5.39%) and St III (16.85%) in terms of their annual percent contribution to the total macrobenthic invertebrates at different stations. St IV ranked second in its percent contribution (22.29%) to the total macrobenthic fauna (Fig. 3). The mean density of molluscs was observed to be highest at St IV (87.75 ind.[m.sup.-2] [+ or -] 86.80) followed by St I (72 ind.[m.sup.-2] [+ or -] 106.43) and St III (57 ind.[m.sup.-2] [+ or -] 78.06). The least density of mollusks was recorded at St II (28.5 ind.[m.sup.-2] [+ or -] 36.53). Maximum molluscan density was documented in August at St I (288 ind.[m.sup.-2]) and St II (126 ind.[m.sup.-2]), June at St III (237 ind.[m.sup.- 2]) and September at St IV (279 ind.[m.sup.-2]) (Fig. 2d).
[FIGURE 2 OMITTED]
Seasonal abundance (ind.[m.sup-2]) of the predominant macrobenthic species in the four stations has been depicted in Fig. 5. The Shannon Index of diversity dropped from 2.667 at St IV to 1.616 at St I (Table 3). Monthly Shannon diversity at different stations has been given in Fig. 6. The species diversity registered significant negative correlations with dominance (r = -0.970, p<0.05), atmospheric temperature (r = 0.533, p<0.05) and chloride (r = -0.713, p<0.05) while it was positively correlated with evenness (r = 0.818, p<0.05), richness (r = 0.968, p<0.05) and transparency (r = 0.518, p<0.05) (Table 4 & 5). Two-Way ANOVA recorded significant temporal variations in diversity between stations ([F.sub.3.33] = 3.314, p<0.05) as well as between months ([F.sub.11,33] = 2.29, p<0.05). Index of dominance was about four times greater at St I (0.378) than at St IV (0.097) (Table 3). Simpson's dominance values exhibited wider monthly variations (Fig. 6). Species dominance showed significant positive correlation with chloride (r = 0.699, p<0.05) and negative correlation with evenness (r = -0.866, p<0.05), richness (r = -0.908, p<0.05) and dominance (r = -0.970, p<0.05) (Table 4 & 5). F-Value registered significant temporal variations in dominance between stations ([F.sub.3,33] = 2.83 8, p<0.05) but recorded insignificant variations between months.
Evenness Index also showed the same trend as that of diversity i.e. a gradual decline from St IV (0.792) to St I (0.458) (Table 3). Pielou's evenness in different months at all the stations has been tabulated in Fig. 6. Evenness registered significant positive correlations with diversity (r = 0.818, p<0.05), richness (r = 0.666, p<0.05) while negative correlation with dominance (r = -0.866, p<0.05) (Table 4 & 5). Two-Way ANOVA recorded significant temporal variation in evenness between stations ([F.sub.3,33] = 4.675, p<0.05) but exhibited insignificant variation between months. The highest Marglefs value of 3.370 was calculated at St III, followed by St I (3.344), St IV (3.309) and St II (2.74) (Table 3). Richness varies monthly at all the stations which have been clearly depicted in Fig. 6. Species richness showed negative significant correlations with dominance (r = -0.908, p<0.05), atmospheric temperature (r = 0.521, p<0.05), carbonates (r = -0.573, p<0.05) and chloride (r = -0.798, p<0.05) whereas significant positive correlation existed with diversity (r = 0.968, p<0.05), evenness (r = 0.666, p<0.05) and transparency (r = 0.623, p<0.05) (Table 4 & 5).
Two-way ANOVA recorded significant temporal variations in richness between months ([F.sub.11.33] = 2.374, p<0.05) but insignificant variations between stations. Figure 7 depicted the scattergrams with fitted regression lines showing linear relationships between changes in macrobenthic density and physico-chemical parameters of the water.
When comparison between stations was made by using qualitative presenceabsence type, Sorenson's Quotient of similarity (Q/S), St I and IV were found more similar with highest value of 81.25% whereas low similarity (73.68%) was calculated between St II and IV. Based on meristic data i.e. counts of individuals referring quantitative indices, Morisita-Horn Index showed maximum values of similarity between St I and II (MH = 0.943) while minimum similarity was found among St I and IV (MH = 0.31) (Table 6). Among macrobenthic community, molluscan density exhibited significant positive correlation with atmospheric temperature (r = 0.572, p<0.05), water temperature (r = 0.695, p<0.05) and depth (r = 0.704, p<0.05) while significant negative correlations was found with pH (r = -0.610, p<0.05), dissolved oxygen (r = -0.623, p<0.05), bicarbonates (r = -0.826, p<0.05), magnesium (r = - 0.926, p<0.05) and chloride (r = -0.520, p<0.05) (Table 4 & 5). Macrobenthic density registered significant temporal variations between stations ([F.sub.3,9] = 4.685, p<0.05) and insignificant annual variations.
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
In Gharana Wetland (Reseve), maximum macrobenthic invertebrate density during autumn may be attributed to the richness of organic sediments as a consequence of allochthonous materials entering the wetland from the catchment area during monsoon (Scott et al, 1928; Srivastava, 1956; Mandal and Moitra, 1975; Vasisht and
Bhandal, 1979)[28,29,30,31]. Bose and Lakra (1994) affirmed that the soft clay soil with decaying leaves and other organic matter in the bottom soil influences the growth and propagation of various benthic animals. They further suggested that the maximum number of most of the species of benthic organisms occurred after monsoon rain, which supports the present observation of having maximum macrobenthic density during post-monsoon period. Spring rise (April) in macrobenthic invertebrate density may be associated with the presence of high organic detritus during this period. Decline in the macrobenthic population recorded in May at all the stations may be the effect of reduced transparency and increased turbidity (Lamptey and Armah, 2008). Moreover, during Pre-monsoon period, the rate of multiplication of macro invertebrates is also reduced (Bose and Lakra, 1994).
The presence of allochthonous detritus sediments enhanced the abundance of detritivores like Oligochaetes (Manoharan et al, 2006) which confirms the peak of annelid population during September at St I and II due to the ingression of allochthonous material into the wetland from catchment area during monsoon rains. On the other hand, St III and IV which harbored thick growth of macrophytes maintained highest density during April as a consequence of organic detritus (Dutta and Malhotra, 1986) resulting from the accelerated rate of decomposition of macrophytes after post-winter rise in temperature. Temperature has been cited as an important environmental factor to cause rapid macrophytic decomposition (Hynes and Kaushik, 1969; Carpenter and Adams, 1979)[36,37]. Decline in the Tubifex tubifex count which ultimately led to the fall of annelid density may be attributed to their consumption by other bottom dwelling predators as also described by Brinkhurst (1974) and Kumar (1997).
Disposal of domestic sewage from village side at St I enhanced organic detritus leading to the highest density of oligochaetes at this station. Abundance of oligochaetes due to greater load of organic detritus has been well opined by Egglishaw and Mackay (1967), Learner et al (1971) and Hawkes (1979). Mukherji et al (1998)[4 ] documented that the predominance of oligochaetes could be attributed to the inflow of sewage as well as the availability of food in the form of decaying organic matter. Abundance of oligochaetes particularly Tubificidae (Yildrim, 2004) in the water mainly polluted by domestic sewage has been well suggested by Carr and Hiltunen (1965), Odum (1971), Mastrantuno (1986) and Navas-Pereira and Henrique (1996).
Oligochaetes particularly Tubifex tubifex are considered as the pollution indicator species (Howmiller and Beeton, 1971; Oliver, 1971; Milbrink, 1980; Bazzanti, 1983; Sturmbauer et al, 1999; and Qadri and Yousuf, 2004)[49,50,51,52,53,54] and a mass occurrence of Tubifex tubifex and Limnodrillus hoffmesteri was usually noted with a density of 3,000-8,000 ind.[m.sup.-2] (Kennedy, 1965). Brinkhurst and Cook (1974)^, Brinkhurst (1975 and 1980)[57,58], McLusky et al (1980), Kazanci (1998), Swayne and Day (2004), Yildiz and Ergonul (2007) and Kucuk (2008) also reported the abundance of Tubificidae (Tubifex tubifex and Limnodrillus hoffmesteri) in organically polluted water. According to Xiong et al (2003), the density of oligochaetes increased significantly with increasing trophic state. Highest density of Oligochaetes at St I clearly depicted that St I was the most polluted station and had higher trophic state as compared to rest of the three stations. Dominance of dipterans at St I and II was mainly contributed by Chironomus sp. which ultimately led to the peak of arthropods during September. This might be owing to the presence of thick layers of soft organically rich sediments as a result of entry of allochthonous material during monsoon rains which is in line with the findings of David and Ray (1966), Edwards et al (1971) and Reid and Wood (1976).
Greater density of Chironomus sp. at St I may be ascribed to the direct entry of domestic sewage. Silva et al (2009) revealed that the predominance of this genus may be associated with discharges of domestic sewage, which causes the increase of organic matter, thereby making the environment more adequate for these organisms. According to Merritt and Cummins (1996), the range of conditions under which chironomids are found in more extensive than that of any other group of aquatic insects and their wide ecological amplitude is related to the very extensive array of morphological, physiological and behavioral adaptations. Moreover, Loden (1974) stated that chironomid larvae can be used as biological indicators. The present observation of having highest density of Chironomus sp. at St I indicate that this station is highly polluted.
Maximum input of Order Coleoptera at St III and IV may be attributed to the thick growth of macrophytes at these stations. Sharma (2002) also recorded higher coleopteran density associated with thick vegetation. Ephemeropterans recorded their complete absence at St III and IV. Comparatively higher density of ephemeropterans at St I as compared to St II may be due to the enrichment of organic detritus at this station which is in contradiction with the findings of Hynes (1960), Bogoescu and Rogaz (1973), Choudhary (1984), Dudgeon (1993) and Kumar (1996) who established an inverse relationship between ephemeropterans and organic load. Langford and Bray (1969) opined that Baetis sp. is a pollution indicator species that exists in organically polluted waters, thereby supporting the present observation. Abundance of odonates during monsoon period at St I, III and IV was directly related to the luxuriant macrophytic growth (Cronin et al, 2006). Macrophytes provide excellent diverse niches for several insect larvae/adult which are adopted for mining into stems and leaves (Mukherji et al, 1998).
Highest molluscan density observed during monsoon period at all the stations may be ascribed to the prolific growth of macrophytes which provided favorable habitat by increasing the available benthic area for molluscan populations (Anderson and Sedell, 1979; Qadri and Yousuf, 2004)[79,54]. Macrophytes provide suitable food and shelter for gastropods (McLachlan, 1975; Soszka, 1975; Maitland, 1978)[80,81,82]. Peak in molluscan density during August at St I and II and September at St IV is in accordance with the results of Malhotra et al, (1996). Maximum molluscan density in June at St III could be attributed to the effect of higher rate of reproduction at higher temperature (Dutta and Malhotra, 1986). Malhotra et al (1996) related the availability of maximum molluscs during summer months to two important ecological phenomena: i) The maximum abundance of decomposer settled organic matter and macrophytes on the bottom of the water body and (ii) Increased water temperature activating the process of decomposition of these organic sediments. Higher abundance of molluscs with increased water temperature and decomposed organic matter has been also reported by Bath et al (1999). Low count of mollusks during winter may be associated with the low water temperature as also described by Dutta and Malhotra (1986), Reece and Richardson (2000), Frisberg et al (2001), Fenoglio et al (2004), Ndaruga et al (2004) and Silviera et al (2006).
Gerritsen et al (1998) stated that as the number and distribution of species (biotic diversity) within the community increases, so does the value of H', which indicates that St IV is more diverse. Moreover, highest Shannon diversity Index value at St IV suggested that this station was able to sustain a richer macrobenthic community as also documented by Albertoni et al (2007). Macrobenthic communities exhibited dominance in only few months and most of the taxa were observed throughout the year as rare taxa. According to Albertoni et al (2007) presence of rare taxa in most of the period indicate good environmental conditions for their development recognized by lower levels of dominance. Mukhopadhyay et al (2007) documented that although both Shannon measures and Simpson's index consider the proportional abundance of species, H' is more sensitive to rare species and 'C' puts more emphasis on the common species. Therefore, it indicates the occurrence of many rare species at St IV as compared to other sites and least species at St I. Krebs (1994) also opined that index of dominance places relatively little weight on rare species and more weight on common species. Dominance was found inversely related to the diversity of the community which is in consonance with the observations of Simpson (1949) and Green (1993) who suggested the same trend.
Xie et al (1996) and Gong and Xie (2001) established a relationship between diversity of macrobenthic community and trophic status of the water body. They demonstrated that the more eutrophic the water body, the lower the macrobenthic species diversity. Other studies in Chinese lakes of different trophic status revealed that eutrophication could result in a remarkable decline in the diversity of macrobenthic taxa which may be explained by the presence of few dominant species, since sensitive organisms are incapable of surviving in extreme conditions (Xiong et al, 2003). Hence, the results indicated that St I is having higher trophic status.
Highest Marglef's species richness index (which considers both abundance and species number) at St III revealed that this site harbored a good number of macrobenthic taxa. Schafer (1980) established a relationship among habitat conditions, dominance and richness. Extreme habitats (eutrophic waters) are characterized by a limited number of adapted species and their high dominance. On the other hand, the habitats having balanced conditions inhabit biocoenosis richness in terms of the number of species and with uniform distribution of individuals. Further, he concluded that high levels of evenness indicate an environment with heterogeneous conditions regulated by a community which is rich in the number of species and the multiplicity of their mutual relationships. Monthly variations in evenness may be the consequence of extremely heterogeneous conditions in some months and simplified in others thereby leading in a simpler way. Low evenness in St I and II may be accounted for by local disturbance due to anthropogenic pressure. Higher evenness values at St III and IV corresponds to stable environmental conditions. Tlig- Zouari and Maamouri-Mokhtar (2008) observed evenness values ranging from 0.60 to 0.83, lower values at disturbed areas while elevated values at stable habitats.
Mathews (1986) concluded that Morisita Horn Index below 0.50 indicate low similarities in the relative abundance of species, whereas index above 0.75 indicate high similarities, thereby confirming the high similarity between St I and II. Michael (1968), Dutta and Malhotra (1986) and Malhotra et al (1996) recorded a positive correlation between molluscs and temperature. Cheatum (1934) and Sharma (1986) have reported an inverse relationship of molluscs with dissolved oxygen and pH.
The information generated from this study gives us a clear picture depicting the effect of intense anthropogenic pressure over the wetland and its macrobenthic fauna, causing a decline in their abundance as well as their diversity. This piece of work will facilitate to fulfill the great need of framing the diverse conservatory strategies for the reduction of direct and indirect forms of anthropogenic influence over the macrobenthic invertebrate community and their habitat.
Authors thankfully acknowledge IARI, New Delhi for authentic identification of the macrobenthic invertebrate taxa.
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K.K. Sharma, *Minakshi Saini and Arti Sharma
Department of Zoology, University of Jammu, Jammu-180006, J&K, India.
E-mail:firstname.lastname@example.org, email@example.com firstname.lastname@example.org
* Corresponding Author E-mail: email@example.com
Table 1. Mean and Standard deviation (N = 12) of the physico-chemical parameters at the stations. Parameter St I St II Air Temp. 30.42 [+ or -] 5.77 30.75 [+ or -] 6.60 ([degrees]C) (16-38) (15-38) Water Temp. 25.67 [+ or -] 5.68 26.83 [+ or -] 6.39 ([degrees]C) (15-34) (14-34) Depth (cm) 28.74 [+ or -] 15.30 38.46 [+ or -] 22.40 (6.5-57) (9-85) Transp. (cm) 14.16 [+ or -] 7.32 19.98 [+ or -] 13.92 (1.5-23.5) (2.2-43) pH 8.51 [+ or -] 0.81 8.53 [+ or -] 0.67 (6.6-9.5) (7.2-9.5) DO (mg/l) 4.24 [+ or -] 2.43 4.07 [+ or -] 1.44 (1.6-8.4) (2-6.4) FC[O.sub.2] 12.5 [+ or -] 11.46 12.17 [+ or -] 10.11 (mg/l) (0-40) (0-34) C[O.sub.3.sup.2-] 7 [+ or -] 23.22 6 [+ or -] 19.90 (mg/l) (0-84) (0-72) HC[O.sub.3.sup.-] 777.75 [+ or -] 223.44 773.18 [+ or -] 265.21 (mg/l) (457.5-1067.5) (414.8-1189.5) [Ca.sup.2+] 36.83 [+ or -] 17.21 37.43 [+ or -] 17.10 (mg/l) (16.04-62.56) (14.44-64.16) [Mg.sup.2+] 55.08 [+ or -] 23.04 49.17 [+ or -] 17.29 (mg/l) (20.90-94.77) (19.44-71.93) [Cl.sup.-] 137.22 [+ or -] 154.19 126.75 [+ or -] 140.10 (mg/l) (19.96-518.96) (23.95-495) Parameter St III St IV Air Temp. 29.5 [+ or -] 7.94 27.58 [+ or -] 9.31 ([degrees]C) (14-39) (14-39) Water Temp. 25.67 [+ or -] 7.32 24.75 [+ or -] 7.29 ([degrees]C) (13-36) (13-35) Depth (cm) 35.84 [+ or -] 19.46 28.48 [+ or -] 14.21 (8.3-74) (12-61) Transp. (cm) 27.64 [+ or -] 18.22 20.08 [+ or -] 12.86 (2.2-58.5) (1.9-38) pH 8.8 [+ or -] 0.75 9.05 [+ or -] 0.54 (6.8-9.6) (7.4-9.6) DO (mg/l) 4.73 [+ or -] 1.95 4.51 [+ or -] 1.94 (1.6-7.6) (2.2-7.6) FC[O.sub.2] 8.83 [+ or -] 9.88 6.5 [+ or -] 8.01 (mg/l) (0-38) (0-32) C[O.sub.3.sup.2-] 35.5 [+ or -] 82.72 48 [+ or -] 108.33 (mg/l) (0-270) (0-324) HC[O.sub.3.sup.-] 692.86 [+ or -] 224.47 685.23 [+ or -] 205.74 (mg/l) (433.1-1067.5) (396.5-988.2) [Ca.sup.2+] 34.82 [+ or -] 12.99 35.09 [+ or -] 13.62 (mg/l) (20.05-56.94) (21.65-62.56) [Mg.sup.2+] 45.16 [+ or -] 14.04 43.46 [+ or -] 14.44 (mg/l) (22.36-66.1) (20.41-64.15) [Cl.sup.-] 140.89 [+ or -] 159.60 91.15 [+ or -] 112.13 (mg/l) (19.96-508.98) (15.96-383.23) Table 2: Density of Macrobenthic Invertebrates (ind.m [+ or -] sd) in the sampling stations. In parentheses is the minimum and maximum value. Species St I St II ANNELIDA Oligochaeta Tubificdae Tubifex tubifex 136.5 [+ or -] 369.36 84 [+ or -] 241.42 (Muller) (0-1350) (0-882) Branchiura sowerbyi 15.75 [+ or -] 32.06 6.75 [+ or -] 16.07 (Beddard) (0-108) (0-54) Limnodrillus 0.75 [+ or -] 2.49 0.75 [+ or -] 2.49 hoffmeisteri (0-9) (0-9) Claparede Hirudinea Glossiphoniidae Helobdella sp. -- -- Blanchard Hirudinidae Hirudinaria -- 2.25 [+ or -] 5.36 granulosa (0-18) (Savigny) ARTHROPODA Insecta Ephemeroptera Baetis sp. Leach 4.5 [+ or -] 10.71 2.25 [+ or -] 7.46 (0-36) (0-27) Odonata Perithemes sp. Hagen 2.25 [+ or -] 5.36 -- (0-18) Enallagma sp. 2.25 5.36 -- Charpentier (0-18) Hemiptera Sphaerodema 0.75 [+ or -] 2.49 2.25 [+ or -] 5.36 annulatum (0-9) (0-18) Fabricius Sphaerodema molestum 6 [+ or -] 9.95 0.75 [+ or -] 2.49 Duf. (0-27) (0-9) Hydrometra greeni -- -- Kirkaldy Laccotrephes 0.75 [+ or -] 2.49 0.75 [+ or -] 2.49 maculates (0-9) (0-9) (Fabricius) Corixa hieroglyphica 12.75 [+ or -] 16.21 12.75 [+ or -] 26.61 Duf. (0-54) (0-90) Plea liturata Fieber 0.75 [+ or -] 2.49 -- (0-9) Notonecta sp. Linne 6.75 [+ or -] 16.07 1.25 [+ or -] 26.78 (0-54) (0-90) Coleoptera Sternolophus rufipes 1.5 [+ or -] 4.97 0.75 [+ or -] 2.49 Fabricius (0-18) (0-9) Regimbartia 0.75 [+ or -] 2.49 4.5 [+ or -] 14.92 attenuata (0-9) (0-54) (Fabricius) Dactylosternum 1.5 [+ or -] 4.97 1.5 [+ or -] 4.97 Wollaston (0-18) (0-18) Berosus pulchellus 65.25 [+ or -] 78.21 32.25 [+ or -] 54.68 Mackleay (0-261) (0-180) Hydrovatus 51 [+ or -] 124.02 34.5 [+ or -] 58.54 acuminatus (0-450) (0-189) Motschulsky Hypophorus sp. Sharp 4.5 [+ or -] 8.62 6 [+ or -] 15.30 (0-27) (0-54) Laccophilus flexusus 2.25 [+ or -] 7.46 6.75 [+ or -] 13.81 (Aube) (0-27) (0-45) Canthydrus 135 [+ or -] 242.33 25.5 [+ or -] 72.08 laetabilis (0-720) (0-261) (Walker) Cybister 0.75 [+ or -] 2.49 -- tripunctatus (0-9) asiaticus (Sharp) Paedrus extraneus 0.75 [+ or -] 2.49 0.75 [+ or -] 2.49 Wied. (0-9) (0-9) Cassida exilis 3 [+ or -] 7.65 -- Boheman (0-27) Hygrobia sp. 0.75 [+ or -] 2.49 -- Latreille (0-9) Diptera Chironomus sp. 958.5 [+ or -] 1551.03 229.5 [+ or -] 289.83 Meigen (0-4581) (0-1089) Pentaneura sp. -- 9 [+ or -] 24.92 Philippi (0-90) Tabanus sp. Linnaeus 7.5 [+ or -] 15.95 -- sens. lat. (0-54) Culicoides sp. 96 [+ or -] 148.58 22.5 [+ or -] 35.34 Latreille (0-495) (0-126) Probezzia sp. 13.5 [+ or -] 33.57 -- Kieffer (0-117) Chaoborus sp. 1.5 [+ or -] 4.97 3 [+ or -] 9.95 Lichtenstein (0-18) (0-36) Odontomyia sp. 0.75 [+ or -] 2.49 -- Meigen (0-9) Tubifera sp. Meigen 0.75 [+ or -] 2.49 -- (0-9) MOLLUSCA Gastropoda Planorbidae Gyraulus sp. 61.5 [+ or -] 95.38 25.5 [+ or -] 31.78 Charpentier (0-270) (0-108) Heliosoma sp. 6 [+ or -] 13.91 3 [+ or -] 6.71 Swainson (0-45) (0-18) Lymnaedae Lymnaea sp. Lamarck 4.5 [+ or -] 10.71 -- (0-36) Viviparidae Viviparus -- -- bengalensis (Lamarck) Species St III St IV ANNELIDA Oligochaeta Tubificdae Tubifex tubifex 67.5 [+ or -] 98.97 60.75 [+ or -] 84.12 (Muller) (0-288) (0-261) Branchiura sowerbyi 6 [+ or -] 13.91 4.5 [+ or -] 10.72 (Beddard) (0-45) (0-36) Limnodrillus 0.75 [+ or -] 2.49 0.75 [+ or -] 2.49 hoffmeisteri (0-9) (0-9) Claparede Hirudinea Glossiphoniidae Helobdella sp. 0.75 [+ or -] 2.49 -- Blanchard (0-9) Hirudinidae Hirudinaria 3.75 [+ or -] 7.76 2.25 [+ or -] 5.36 granulosa (0-27) (0-18) (Savigny) ARTHROPODA Insecta Ephemeroptera Baetis sp. Leach -- -- Odonata Perithemes sp. Hagen 1.5 [+ or -] 3.35 -- (0-9) Enallagma sp. 4.5 [+ or -] 12.46 4.5 [+ or -] 10.71 Charpentier (0-45) (0-36) Hemiptera Sphaerodema 8.25 [+ or -] 13.97 2.25 [+ or -] 5.36 annulatum (0-45) (0-18) Fabricius Sphaerodema molestum 6.75 [+ or -] 11.69 4.5 [+ or -] 5.81 Duf. (0-36) (0-18) Hydrometra greeni 1.5 [+ or -] 4.97 2.25 [+ or -] 5.36 Kirkaldy (0-18) (0-18) Laccotrephes 0.75 [+ or -] 2.49 2.25 [+ or -] 5.36 maculates (0-9) (0-18) (Fabricius) Corixa hieroglyphica 6.75 [+ or -] 19.83 25.5 [+ or -] 39.20 Duf. (0-72) (0-108) Plea liturata Fieber -- 1.5 [+ or -] 4.97 (0-18) Notonecta sp. Linne 6 [+ or -] 13.91 18 [+ or -] 24.09 (0-45) (0-72) Coleoptera Sternolophus rufipes -- -- Fabricius Regimbartia 3.75 [+ or -] 8.58 0.75 [+ or -] 2.49 attenuata (0-27) (0-9) (Fabricius) Dactylosternum -- 1.5 [+ or -] 4.97 Wollaston (0-18) Berosus pulchellus 45.75 [+ or -] 85.26 34.5 [+ or -] 64.36 Mackleay (0-315) (0-243) Hydrovatus 15 [+ or -] 23.33 24 [+ or -] 48.79 acuminatus (0-72) (0-153) Motschulsky Hypophorus sp. Sharp 1.5 [+ or -] 4.97 10.5 [+ or -] 13.16 (0-18) (0-36) Laccophilus flexusus 4.5 [+ or -] 8.62 19.5 [+ or -] 28.89 (Aube) (0-27) (0-108) Canthydrus 68.25 [+ or -] 95.07 35.25 [+ or -] 62.08 laetabilis (0-288) (0-189) (Walker) Cybister -- -- tripunctatus asiaticus (Sharp) Paedrus extraneus 0.75 [+ or -] 2.49 2.25 [+ or -] 5.36 Wied. (0-9) (0-18) Cassida exilis -- 0.75 [+ or -] 2.49 Boheman (0-9) Hygrobia sp. -- - Latreille Diptera Chironomus sp. 12 [+ or -] 23.62 24 [+ or -] 44.29 Meigen (0-72) (0-144) Pentaneura sp. 2.25 [+ or -] 5.36 -- Philippi (0-18) Tabanus sp. Linnaeus -- 3 [+ or -] 5.61 sens. lat. (0-18) Culicoides sp. 10.5 [+ or -] 15.95 17.25 [+ or -] 26.36 Latreille (0-45) (0-81) Probezzia sp. 1.5 [+ or -] 4.97 2.25 [+ or -] 7.46 Kieffer (0-18) (0-27) Chaoborus sp. -- 1.5 [+ or -] 4.97 Lichtenstein (0-18) Odontomyia sp. 0.75 [+ or -] 2.49 -- Meigen (0-9) Tubifera sp. Meigen -- -- MOLLUSCA Gastropoda Planorbidae Gyraulus sp. 54 [+ or -] 78.20 75.75 [+ or -] 79.61 Charpentier (0-234) (0-261) Heliosoma sp. 0.75 [+ or -] 2.49 -- Swainson (0-9) Lymnaedae Lymnaea sp. Lamarck 2.25 [+ or -] 5.36 3 [+ or -] 5.61 (0-18) (0-18) Viviparidae Viviparus -- 9 [+ or -] 16.02 bengalensis (0-54) (Lamarck) Table 3: Diversity Indices of macrobenthic invertebrate community in the stations. Diversity Indices St I St II St III St IV Shanon-Weaver Index 1.616 2.011 2.421 2.667 Simpson's Index 0.378 0.230 0.131 0.097 Marglef's Index 3.344 2.741 3.249 3.309 Pielou's Index 0.458 0.566 0.727 0.792 Table 4: Correlation coefficient (significant at p<0.05) between various diversity indices (* marked correlations are significant). Dominance Evenness Richness Diversity -0.970 * 0.818 * 0.968 * Dominance -0.866 * -0.908 * Evenness 0.666 * Richness Table 5: Correlation coefficient (significant at p<0.05) between the community characteristics and physico-chemical parameters of their habitat (* marked correlations are significant). Annelida Arthropoda Mollusca Total Benthos Air 0.204 -0.452 0.506 * -0.296 Temperature Water 0.214 -0.147 0.695 * -0.010 Temperature Depth -0.013 0.085 0.704 * 0.141 Transparency -0.080 0.255 0.258 0.229 pH 0.021 0.351 -0.610 * 0.248 Dissolved -0.228 0.138 -0.623 * 0.006 Oxygen Free Carbon -0.002 -0.426 0.406 -0.330 Dioxide Carbonates 0.059 -0.230 -0.370 -0.223 Bicarbonates 0.208 0.110 -0.826 * 0.060 Calcium -0.304 0.229 -0.577 * 0.072 Magnesium 0.009 0.083 -0.926 * -0.018 Chloride -0.096 -0.307 -0.520 * -0.340 Diversity Dominance Evenness Richness Air -0.533 * 0.480 -0.427 -0.521 * Temperature Water -0.450 0.383 -0.378 -0.437 Temperature Depth 0.303 -0.327 0.063 0.399 Transparency 0.518 * -0.476 0.174 0.623 * pH 0.327 -0.216 0.067 0.366 Dissolved 0.164 -0.141 0.324 0.096 Oxygen Free Carbon -0.305 0.202 0.020 -0.377 Dioxide Carbonates -0.419 0.307 0.022 -0.573 * Bicarbonates -0.198 0.191 0.015 -0.302 Calcium 0.115 -0.033 -0.052 0.222 Magnesium -0.082 0.142 -0.007 -0.151 Chloride -0.713 * 0.699 * -0.361 -0.798 * Table 6. Different similarity indices to compare the community structure of the stations. Compared Stations Sorenson's Quotient Morisita-Horn Index St I vs. St II 80% 0.943 St I vs. St III 79.37% 0.311 St I vs. St IV 81.25% 0.310 St II vs. St III 79.25% 0.438 St II vs. St IV 73.68% 0.489 St III vs. St IV 80.70% 0.890 Figure 4: Relative abundance of various orders of arthropoda of four stations. ST I Coleoptera 19.44% Odonata 0.36% Ephemeroptera 0.32% Diptera 77.69% Hemiptera 2.19% ST II Coleoptera 28.03% Hemiptera 7.04% Diptera 64.32% Ephemeroptera 0.61% ST III Coleoptera 67.94% Hemiptera 3.35% Diptera 13.16% Ephemeroptera 15.55% ST IV Coleoptera 54.54% Hemiptera 1.82% Diptera 20.00% Ephemeroptera 23.64%