Assessment of macroinvertebrate diversity and water quality of the Malaprabha river near Munavalli, Belagavi district, Karnataka state, India

J. Biodiv. & Environ. Sci. Shavi and Sanakal RESEARCH PAPER OPEN ACCESS Assessment of macroinvertebrate diversity and water quality of the Malaprabha river near Munavalli, Belagavi district, Karnataka state, India Mr. Shama Shavi, Rajeshwari D. Sanakal* Department of Zoology, Karnataka Science College, Dharwad, Karnataka, India Key words: Macroinvertebrates, Water quality, Malaprabha river, Munavalli, Biodiversity DOI: https://dx.doi.org/10.12692/jbes/27.5.12-24 [ Published: November 04, 2025 ] ABSTRACT This research examines the relationship between the diversity of macroinvertebrate species and water quality in the Malaprabha river near Munavalli, Savadatti taluk, Belagavi district, Karnataka, India. Seasonal assessments of macroinvertebrate communities were conducted over one year (November 2021–October 2022) at five designated sampling sites (S1–S5) using the Kick Net method. A total of 24 species were identified, representing three phyla: Annelida (2 species), Arthropoda (15 species), and Mollusca (7 species). Arthropoda was the most dominant phylum, while the presence of pollution indicator species such as Chironomus larvae, Limnodrilus sp., and Lymnaea sp. reflected pollution levels in the river ecosystem. Diversity indices and correlations between macroinvertebrate abundance and sixteen water quality variables were evaluated using Canonical Correspondence Analysis (CCA) in PAST software. Interrelationships among physico-chemical parameters were examined using Pearson’s correlation coefficient in SPSS (IBM, Version 21). The results indicate that variations in water quality have a significant influence on macroinvertebrate assemblages. *Corresponding Author: Rajeshwari D. Sanakal  sanakalra[email protected]m Journal of Biodiversity and Environmental Sciences | JBES ISSN: 2220-6663 (Print); 2222-3045 (Online) Website: https://www.innspub.net E-mail contact: [email protected] Vol. 27, Issue: 5, p. 12-24, 2025 J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 13 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net INTRODUCTION Macroinvertebrates are visible, invertebrate aquatic organisms that inhabit riverine environments. They represent a vital component of freshwater ecosystems and are widely recognized as reliable indicators of stream and river health. Some species are sensitive to pollution, while others are able to tolerate degraded conditions. Variations in their community structure and abundance provide insight into water quality (Bonada et al., 2006). These organisms are taxonomically diverse and relatively long-lived, exhibiting measurable responses to anthropogenic impacts on aquatic systems (Sharma and Chaudhary, 2011). Most benthic forms feed on detritus deposited on the substrate, thereby serving as an important food source for several fish species (Imevbore and Bakare, 1970; Adebisi, 1989; Ajao, 1990; Oke, 1990; Idowu and Ugwumba, 2005). Furthermore, they enhance the breakdown of organic materials into simpler nutrients such as nitrates and phosphates (Gallep et al., 1978). Consequently, macroinvertebrates occupy a crucial position in the aquatic food web, supporting higher trophic levels including fish, birds, and mammals (Bernes and Hughes, 1988). Macroinvertebrates offer a more precise and enduring reflection of evolving aquatic conditions compared to chemical and microbiological assessments (Ravera, 1998, 2000; Ikomi et al., 2005). The study of macroinvertebrates is one of the most widely accepted biological methods for evaluating freshwater bodies affected by industrial wastewater (Odiete, 1999). The diversity, abundance, and spatial distribution of macroinvertebrates are significantly influenced by various water quality parameters (Imevbore, 1967; Haslam, 1990; APHA/WWA/WEF, 1998; Odiete, 1999). Studies have demonstrated that shifts in macroinvertebrate community structure often reflect alterations in local environmental conditions, serving as valuable indicators for assessing the ecological health of aquatic ecosystems. Extensive research has been conducted on freshwater macroinvertebrates in India, including studies by Srivastava (1956), Krishnamurthy (1966), Dev et al. (1993), Mandal and Moitra (1975), Raman et al. (1976), Gupta (1976), Misra et al. (1981), Gupta and Pant (1983), and Barbhuiyan and Khan (1992). However, there is a notable gap in the literature regarding the macroinvertebrate fauna of the Malaprabha River in Munavalli Town, Belagavi District, Karnataka. This river is a vital resource for the local community, providing water for drinking, irrigation, recreation, and fishing. Despite its significance, the river faces pollution challenges from various anthropogenic activities. These include industrial discharges, agricultural runoff, and sewage contamination, which degrade water quality. Additionally, practices such as bathing, cloth washing, animal washing, vehicle washing, idol immersion, floral offerings, and human waste disposal further contribute to the pollution, compromising the river's ecological health. The primary aim of this study is to assess the diversity of macroinvertebrates and investigate how their distribution correlates with the physico-chemical characteristics of selected sites along the Malaprabha River in Munavalli Town, Belagavi District, Karnataka. MATERIALS AND METHODS Study area The Malaprabha River is one of the prominent rivers in North Karnataka and serves as a tributary of the Krishna River. It originates in the Western Ghats at Kanakumbi village, located at 15°42'20" North latitude and 74°13'9" East longitude. The selected study area is near Munavalli along the Malaprabha River, situated at 15°51'13" North latitude and 75°7'13" East longitude (Map B). Macroinvertebrate assemblages in the Malaprabha River were assessed seasonally over a one-year period from November 2021 to October 2022. Five sampling sites—S1, S2, S3, S4, and S5—were chosen for macroinvertebrate collection (Map C1 and C2) (Fig. 1). J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 14 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net Fig. 1. Study area Map A: Karnataka districts map, Map B: Belagavi district map showing Malaprabha river (Source: dmaps.com), Map C1 & C2: Location of the sampling sites near Munavalli, Savadatti taluk, Belagavi district, Karnataka (Source: Google map) Methodology Macroinvertebrate sampling was carried out seasonally at three time intervals: winter (November 2021 to February 2022), summer (March to June 2022), and monsoon (July to October 2022). Sampling was always carried out between 10:00 AM and 4:00 PM. The Kick Net method was employed for macroinvertebrate collection. This technique involves positioning a ―D‖ frame net in the direction of water flow and the riverbed was disturbed by kicking to dislodge organisms, which were carried into the net. The collected material was poured into a shallow (≈2 cm depth) tray of clean water to allow sediment to settle. Macroinvertebrates were observed moving in the water and carefully removed with forceps, a dropper, or a small spoon. Specimens were then transferred to J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 15 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net pre-labeled, wide-mouthed containers and preserved in a 10% formalin solution. In the lab, specimens were sorted and identified to species level using established taxonomic keys (Edmondson, 1959; Tonapi, 1980; Subba Rao, 1989; Pennak, 1989; Naidu, 2005), and photographic records were taken. At the same time, water samples were collected in clean, sterilized 1-liter polyethylene bottles. Field measurements of pH and temperature were made on site, and other parameters-including turbidity, dissolved oxygen (DO), biological oxygen demand (BOD), total dissolved solids (TDS), electrical conductivity (EC), nitrate, sulfate, chloride, total hardness (TH), calcium, magnesium, sodium, potassium, and ironwere analyzed in the laboratory, following standard procedures outlined by APHA (1985). RESULTS In the current study, 24 macroinvertebrate species were documented across five sampling locations (S1 through S5). These species spanned three principal invertebrate phyla: Annelida (8.33 %), Arthropoda (62.5 %), and Mollusca (29.16 %). These species were classified into 06 classes, 13 orders, and 21 families (Table 1 and Fig. 2). Among them, the phylum Arthropoda was the most dominant, contributing 62.50% of the total macroinvertebrate fauna. It consisted of 15 species from eight orders across three classes. Class Malacostraca (subphylum: Crustacea) accounted for 12.50% of the total macroinvertebrate fauna, represented by two orders—Decapoda and Isopoda—with three families: Palaemonidae, Gecarcinucidae, and Aegidae (Table 1 and Fig. 2). Class Arachnida contributed 4.16% of the total macroinvertebrate fauna, consisting of a single order, Araneae, represented by the family Dolomedidae (Table 1 and Fig. 2). Class Insecta was the single most abundant group among the macroinvertebrates, making up 45.83% of all individuals sampled. The orders Diptera and Odonata were especially prominent. Diptera accounted for 12.50% of the total macroinvertebrate fauna, with representatives from the Culicidae, Muscidae, and Chironomidae families. Similarly, Order Odonata also contributed 12.50%, represented by three families: Libellulidae, Gomphidae, and Coenagrionidae. Order Hemiptera accounted for 8.33%, with two families: Corixidae and Notonectidae. Order Ephemeroptera represented another 8.33%, comprising families Baetidae and Caenidae. Order Coleoptera made up 4.16%, represented by the family Dysticidae (Table 1 and Fig. 3). In this study, the phylum Mollusca was the second most prevalent group, comprising 29.16% of the total macroinvertebrate population. This phylum included six species from the class Gastropoda (25%) and one species from the class Bivalvia (4.16%) (Table 1 and Fig. 3). Gastropods showed dominance over bivalves, consisting of three orders: Architaenioglossa (16.66%), Neotaenioglossa (4.16%), and Basommatophora (4.16%). The order Architaenioglossa was represented by two families: Viviparidae and Ampullariidae. Neotaenioglossa included one family, Thiaridae, while Basommatophora was represented by the family Lymnaeidae. The class Bivalvia was represented by order Unionida, belonging to the family Unionidae. Phylum Annelida contributed 8.33% of the total macroinvertebrate fauna, comprising two species from class Clitellata (8.33%), which belonged to order Tubificida of the family Naididae (Table 1 and Fig. 2 and 2). Table 2 presents the seasonal fluctuations in various physico-chemical parameters of the Malaprabha River from November 2021 to October 2022. Throughout the study period, water temperature fluctuated between a minimum of 26.8°C in winter and a maximum of 37°C in summer. pH levels measured between 6.6 in winter and 7.2 during the monsoon season. J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 16 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net Table 1. Macroinvertebrate fauna identified in river Malaprabha (From November 2021 to October 2022), Munavalli, Dist.-Belagavi, State-Karnataka, India Phylum Class Order Family Genus and species Annelida Clitellata Tubificida Naididae Tubifex tubifex Limnodrilus sp. Arthropoda Malacostraca (Subphylum: Crustacea) Decapoda Palaemonidae Macrobrachium sp. Gecarcinucidae Barytelphusa sp. Isopoda Aegidae Alitropus typus Arachnida Araneae Dolomedidae Dolomedes sp. Insecta Coleoptera Dytiscidae Laccophilus sp. Hemiptera Corixidae Corixa sp. Notonectidae Notonecta sp. Diptera Culicidae Culex larvae Muscidae Limnophora sp. Chironomidae Chironomous sp. Odonata Libellulidae Dragonfly nymph (Libellula sp.) Gomphidae Dragonfly nymph (Gomphus sp.) Coenagrionidae Damsefly nymph sp. Ephemeroptera Baetidae Baetis sp. Caenidae Caenis sp. Mollusca Gastropoda Architaenioglossa Viviparidae Bellamya dissimilis Bellamya bengalensis Vivipara bengalensis Ampullariidae Pila globosa Neotaenioglossa Thiaridae Melanoides sp. Basommatophora Lymnaeidae Lymnaea sp. Bivalvia Unionida Unionidae Lamellidens sp. Fig. 2. Proportional representation of macroinvertebrate phyla Fig. 3. Proportional representation of invertebrate classes Turbidity varying from 4.42 NTU in summer to 22.4 NTU in the monsoon. Dissolved oxygen (DO) concentrations fluctuated between 6.6 mg/L in summer and 7.2 mg/L in the monsoon. Biochemical oxygen demand (BOD) covered a spectrum from 5.9 mg/L in winter to 7.1 mg/L in summer. Total dissolved solids (TDS) varied from 101 mg/L in the monsoon to 150 mg/L in summer. Electrical conductivity (EC) ranged between 208 µS/cm in the monsoon and 280 µS/cm in summer. Nitrate concentrations varying from 1.1 mg/L in summer to 2.5 mg/L in the monsoon. Sulfate levels fluctuated between 17 mg/L in the monsoon and 23 mg/L in summer. Chloride content measured between 20 mg/L in the monsoon and 35 mg/L in summer. Total hardness (TH) levels differed from 78 mg/L in the monsoon to 126 mg/L in summer. Calcium concentrations varied from 22 mg/L in the monsoon to 37 mg/L in summer, while magnesium levels ranged from 7 mg/L in the monsoon to 11 mg/L in winter. Sodium concentrations ranged from 15 mg/L in the monsoon to 28 mg/L in summer and potassium from 2.3 mg/L in winter to 2.8 mg/L in the monsoon. Iron was the least concentrated element in the river, with levels ranging from a minimum of 0.2 mg/L in summer to a maximum of 1.51 mg/L during the monsoon. J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 17 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net Table 2. Seasonal water quality variables, minimum, maximum, mean, and standard deviation of the physicochemical characteristics of water samples from the Malaprabha river (November 2021 to October 2022), Munavalli, Belagavi district, Karnataka, India Parameters Winter Summer Monsoon Min. Max. Mean±SD Temp ( 0 C ) 26.8 37 27 26.8 37 30.26±5.83 pH 6.6 6.8 7.2 6.6 7.2 6.86±0.30 Turbidity (NTU) 5.1 4.42 22.4 4.42 22.4 10.64±10.19 DO (mg/l) 6.8 6.6 7.2 6.6 7.2 6.86±0.30 BOD (mg/l) 5.9 7.1 6.2 5.9 7.1 6.4±0.62 TDS (mg/l) 115 150 101 101 150 122±25.23 EC ( mS/cm) 220 280 208 208 280 236±38.5 No3 (mg/l) 2.1 1.1 2.5 1.1 2.5 1.9±0.72 So4 (mg/l) 18 23 17 17 23 19.3±3.21 Cl (mg/l) 23 35 20 20 35 26±7.93 TotalHardness (mg/l) 99 126 78 78 126 101±24.06 Ca (mg/l) 26 37 22 22 37 28.3±7.76 Magnesium (mg/l) 11 10 7 7 11 9.3±2.08 Sodium (mg/l) 18 28 15 15 28 20.3±6.80 Potassium (mg/l) 2.3 2.5 2.8 2.3 2.8 2.5±0.25 Fe (mg/l) 0.43 0.2 1.51 0.2 1.51 0.71±0.69 NTUNephelometric Turbidity Unit, EC - mS/cm (MicroSiemens/Centimeter Table 3. Correlation coefficients (r) between macroinvertebrates and physico-chemical characteristics of water samples from the Malaprabha River (November 2021 to October 2022), Munavalli, Belagavi district, Karnataka, India Parameters Annelida Arthropoda Mollusca Temp ( °C ) .017 -.973** .987** pH .982*** .396 -.013 Turbidity (NTU) .849** .699* -.371 DO (mg/l) .655* .879** -.629* BOD (mg/l) .240 -.896** .998* TDS (mg/l) -.277 -.998*** .897** EC ( mS/cm) -.156 -.998*** .945*** NO3 (mg/l) .277 .998*** -.897** SO4 (mg/l) -.156 -.998*** .945*** Cl (mg/l) -.189 -1.000*** .933*** Total Hardness (mg/l) -.436 -.973** .809** Ca (mg/l) -.257 -.999* .906*** Magnesium (mg/l) -.961*** -.478 .104 Sodium (mg/l) -.220 -1.000*** .921*** Potassium (mg/l) .993** .326 .062 Fe (mg/l) .772** .787** -.489 */**= Indicates moderately correlated and significant at the 0.05 level (2-tailed), ***= Indicates highly correlated and significant at the 0.05 level (2-tailed). The relationship between physico-chemical parameters and macroinvertebrate density was analyzed, as summarized in Table 3. The Annelida phylum exhibited a highly significant positive correlation with pH levels, a moderately significant positive correlation with turbidity, dissolved oxygen, potassium, and iron concentrations, and a highly significant negative correlation with magnesium levels. Arthropoda displayed a highly significant positive correlation with nitrate levels, a moderately significant positive correlation with turbidity, dissolved oxygen, and iron concentrations. In contrast, it exhibited a highly significant negative correlation with total dissolved solids, electrical conductivity, sulfate, chloride, and sodium levels, and a moderately significant negative correlation with temperature, biochemical oxygen demand, total hardness, and calcium concentrations. Mollusca showed a highly significant positive correlation with EC, sulfate, chloride, calcium, and sodium, a moderately significant positive correlation with Temperature, BOD, TDS and total hardness, and a moderately significant negative correlation with DO and nitrate. J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 18 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net Table 4. Seasonal population density of macroinvertebrates (individuals/m²) at different sites in the Malaprabha river, Munavalli, Belagavi district, Karnataka, India (November 2021 – October 2022) Macroinvertebrates Winter Summer Monsoon S1 S2 S3 S4 S5 Total S1 S2 S3 S4 S5 Total S1 S2 S3 S4 S5 Total Annelida Tubifex tubifex 0 0 0 0 0 0 1 1 0 0 0 02 0 0 0 0 0 00 Limnodrilus sp. 0 0 0 0 0 0 0 0 0 0 0 00 3 0 0 0 1 04 Total 0 0 0 0 0 0 1 1 0 0 0 02 3 0 0 0 1 04 Arthropoda Macrobrachium sp. 1 1 0 0 0 02 0 0 0 0 1 01 0 0 0 0 0 00 Barytelphusa sp. 0 0 0 0 0 00 0 0 0 0 0 00 1 0 0 0 0 01 Alitropus typus 0 0 0 0 0 00 0 0 0 0 0 00 0 0 1 1 0 02 Dolomedes sp. 0 0 0 1 1 02 0 0 0 0 0 00 0 0 1 0 0 01 Laccophilus sp. 0 0 0 0 0 00 0 0 0 0 0 00 1 1 0 0 0 02 Corixa sp. 0 0 1 4 0 05 1 1 1 0 1 04 2 4 1 4 0 11 Notonecta sp. 0 0 0 0 0 00 0 0 0 0 0 00 1 0 0 0 0 01 Culex larvae 0 1 0 0 0 01 0 0 0 0 0 0 0 3 0 0 0 03 Limnophora sp. 0 0 0 0 0 00 0 1 0 0 0 01 0 0 0 0 0 00 Chironomous sp. 5 1 6 0 3 15 1 0 0 0 1 02 0 4 0 0 1 05 Dragonfly nymph (Gomphus sp.) 2 0 0 1 0 03 0 0 0 0 0 00 0 1 0 0 0 01 Dragonfly nymph (Libellula sp.) 0 0 0 2 0 02 0 1 0 0 1 02 1 0 0 0 0 01 Damselfly nymph sp. 0 2 1 0 0 03 0 0 0 0 0 00 0 0 1 0 0 01 Baetis sp. 0 1 0 0 2 03 0 0 0 0 0 00 0 0 0 0 0 00 Caenis sp. 1 0 0 0 2 03 2 0 0 1 2 05 0 0 0 10 7 17 Total 09 06 08 08 08 39 04 03 01 01 06 15 06 13 04 15 08 46 Mollusca Bellamya dissimilis 0 0 0 1 2 03 0 0 0 2 1 03 0 0 0 0 0 00 Bellamya bengalensis 1 1 0 0 1 03 0 0 0 1 1 02 0 0 1 0 0 01 Vivipara bengalensis 0 3 0 2 0 05 14 5 1 0 3 23 2 2 1 1 8 14 Melanoides sp. 0 0 1 0 0 01 3 3 1 2 3 12 2 2 3 1 1 09 Pila globosa 1 1 0 6 0 08 0 1 0 0 1 02 1 1 1 2 0 05 Lymnaea sp. 1 1 0 1 0 03 0 2 0 0 1 03 0 0 0 1 0 01 Lamellidens sp. 1 0 0 3 3 07 7 1 1 5 3 17 1 2 0 0 3 06 Total 04 06 01 13 06 30 24 12 03 10 13 62 06 07 06 05 12 36 The population density of macroinvertebrates (individuals/m²) recorded at various sites during different seasons is summarized in Table 4. Arthropoda emerged as the most, predominant phylum in the study area, comprising 100 individuals from 15 species. Of these, 46 individuals were recorded during the monsoon, 39 during winter, and 15 during the summer season. Among arthropods, insects represented the most dominant subgroup, accounting for 89 out of the 100 individuals. Within this group, Caenis sp. was the most abundant species, with a total of 25 individuals—17 recorded during the monsoon (sites S4 and S5), five during the summer (sites S1, S4, and S5), and three during winter (sites S1 and S5). Chironomus sp. was the second most abundant species, with 22 individuals—15 collected during winter (sites S1, S2, S3, and S5), five in the monsoon (sites S2 and S5), and two in summer (sites S1 and S5). Corixa sp. ranked third in abundance, with 20 individuals recorded—11 during the monsoon across all sites except S5; 5 in winter at sites S3 and S4; and 4 in summer at all sites except S4. Other insect species observed included Laccophilus sp. (2 individuals), Notonecta sp. (1 individual), Culex larvae (4 individuals), Limnophora sp. (1 individual), dragonfly nymphs (Gomphus sp., 4 individuals); Libellula sp. (5 individuals), damselfly nymphs (4 individuals), and Baetis sp. (3 individuals). The class Malacostraca was represented by three species: Macrobrachium sp. (3 individuals), Barytelphusa sp. (1 individual), and Alitropus typus (2 individuals). The class Arachnida included only a single species, Dolomedes sp., with 3 individuals recorded. J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 19 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net Table 5. Diversity indices of macroinvertebrates in the study area Annelida Arthropoda Mollusca Taxa_S 2 15 7 Individuals 6 100 128 Dominance_D 0.5556 0.162 0.2133 Simpson_1-D 0.4444 0.838 0.7867 Shannon_H 0.6365 2.148 1.705 Evenness_e^H/S 0.9449 0.5711 0.7863 From the phylum Annelida, two species were observed: Tubifex tubifex and Limnodrilus sp. Two individuals of Tubifex tubifex were recorded during the summer season at sites S1 (1 individual) and S2 (1 individual), with no presence during the monsoon or winter. Four individuals of Limnodrilus sp. were recorded during the monsoon at sites S1 (3 individuals) and S5 (1 individual). The phylum Mollusca was the second most dominant group in the study, with 128 individuals from 7 species. Of these, 62 individuals were collected during summer, 36 during the monsoon, and 30 during winter. Gastropods were the most dominant subgroup within this phylum, comprising 64 individuals. Vivipara bengalensis was the most abundant gastropod species, with a total of 42 individuals—In summer, 23 individuals were observed across all sites except S4; during the rainy season, 14 individuals were recorded at all sites; and in winter, 5 individuals were found at sites S2 and S4. Melanoides sp. was the next most abundant, with 22 individuals—12 in summer (all sites), 9 during the rainy season (same sites), and 1 in winter (S3). Other gastropod species included Pila globosa (15 individuals), Lymnaea sp. (7 individuals), Bellamya bengalensis (6 individuals), and Bellamya dissimilis (6 individuals). The class Bivalvia was represented by a single species, Lamellidens sp., which was the second most abundant mollusc overall. It totaled 30 individuals—17 in summer (sites S1 to S5), 7 in winter (sites S1, S4, and S5), and 6 during the monsoon (sites S1, S2, and S5). Diversity indices Arthropoda showed the highest species diversity as measured by the Shannon index (2.14), whereas Annelida had the lowest (0.63). Likewise, Simpson’s index was greatest for Arthropoda (0.83) and lowest for Annelida (0.44). Simpson's dominance index showed the lowest dominance (0.162) for Arthropoda, indicating higher diversity, and the highest dominance (0.5556) for Annelida, indicating lower diversity. The evenness index for Annelida (0.9449) was nearly equal to 1, indicating that Annelida were more evenly distributed (despite low richness) than Arthropoda (0.5711) (Table 5). Canonical correspondence analysis (CCA) CCA is a multivariate ordination technique applied to relate species assemblages to environmental (physicochemical) variables. In this investigation, the first axis (horizontal) accounted for 57.3 % of the relationship between species and environment, and the second axis (vertical) accounted for 42.7 %, indicating the extent to which environmental gradients shape macroinvertebrate distribution. The eigenvalues associated with each axis reflect how much of the explained variance each axis carries, with a larger eigenvalue denoting a stronger contribution. In our data, Axis 1 captured the greater proportion of variation in the species–environment relationships. The p-value denotes the statistical significance of the overall correlation: typically p ≤ 0.05 is considered significant. In this study, the p-value was not significant, which supports the null hypothesis that there is no meaningful association between the sets of variables (Table 6). The graphical CCA biplot depicts environmental parameters as vectors (arrows) and species as points (Fig. 3). Table 6. Eigen values for CCA in the study area Axis Eigenvalue Percentage computation (%) p 01 0.27829 57.3 0.53 02 0.20735 42.7 0.699 Species composition and environmental variables showed both positive and negative responses, reflecting variations at the study site. Water temperature was positively associated with BOD, TDS, EC, sulfate, chloride, calcium, sodium, and Lamellidens sp., and negatively associated with DO, J. Biodiv. & Environ. Sci. Vol. 27, Issue: 5, p. 12-24, 2025 20 Shavi and Sanakal Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net nitrate, potassium, Dolomedes sp., and Pila globosa. pH showed a positive response to turbidity, potassium, Barytelphusa sp., Alitropus typus, Laccophilus sp., Notonecta sp., and Caenis sp., but a negative response to magnesium, Macrobrachium sp., Bellamya bengalensis, and Lymnaea sp. Turbidity was positively related to pH, DO, potassium, Fe, Limnodrilus sp., Barytelphusa sp., Alitropus typus, Laccophilus sp., Corixa sp., Notonecta sp., Culex larvae, and Caenis sp., but negatively associated with magnesium, dragonfly nymph (Libellula sp.), Bellamya dissimilis, and Lymnaea sp. Fig. 3. CCA in the study area Dissolved oxygen (DO) was positively correlated with turbidity, nitrate, Fe, Barytelphusa sp., Alitropus typus, Laccophilus sp., Corixa sp., Notonecta sp., and Culex larvae, and negatively with temperature, TDS, total hardness, dragonfly nymph (Libellula sp.), Bellamya dissimilis, and Lymnaea sp. Biological oxygen demand (BOD) showed positive responses to temperature, EC, sulfate, chloride, Tubifex sp., Limnophora sp., Vivipara bengalensis, Melanoides sp., and Lamellidens sp., and negative responses to nitrate, Dolomedes sp., and Pila globosa. Total dissolved solids (TDS) were positively related to temperature, EC, chloride, total hardness, calcium, sodium, Tubifex sp., Limnophora sp., and Lamellidens sp., and negatively to DO, nitrate, Fe, and Culex larvae. Electrical conductivity (EC) showed positive associations with temperature, BOD, TDS, sulfate, chloride, total hardness, calcium, sodium, Tubifex sp., Limnophora sp., and Lamellidens sp., and negative associations with nitrate, Culex larvae, Dolomedes sp., and Pila globosa. Nitrate demonstrated a positive association with dissolved oxygen, iron, and Culex larvae, whereas it was negatively associated with temperature, BOD, TDS, electrical conductivity, sulfate, chloride, total hardness, calcium, sodium, and the taxa Tubifex sp., Limnophora sp., and Lamellidens sp. Sulfate showed positive relationships with temperature, BOD, EC, chloride, total hardness, calcium, sodium, Tubifex sp., Limnophora sp., and Lamellidens sp., and negative relationships with nitrate, Fe, Dolomedes sp., and Pila globosa. Chloride was positively related to temperature, BOD, TDS, EC, sulfate, total hardness, calcium, sodium, Tubifex sp., Limnophora sp., and Lamellidens sp., and negatively related to nitrate, Fe, Dolomedes sp., and Pila globosa. Total hardness exhibited positive associations with TDS, EC, sulfate, chloride, calcium, magnesium, sodium, Limnophora sp., and Lamellidens sp., and negative associations with DO, nitrate, Fe, Culex larvae, Alitropus typus, and Notonecta sp. Calcium was positively related to temperature, TDS, EC, sulfate, chloride, total hardness, sodium, Tubifex sp., Limnophora sp., and Lamellidens sp., and negatively to nitrate, Fe, and Culex larvae. Magnesium responded positively to total hardness, Macrobrachium sp., dragonfly nymph (Libellula sp.), Bellamya bengalensis, and Lymnaea sp., but negatively to pH, turbidity, potassium, Fe, Limnodrilus sp., Barytelphusa sp., Laccophilus sp., Corixa sp., Notonecta sp., and Caenis sp. Sodium showed positive relationships with temperature, TDS, EC, sulfate, chloride, total hardness, calcium, Tubifex sp., and Lamellidens sp., and negative relationships with nitrate, Dolomedes sp., Corixa sp., Pila globosa, and Culex larvae. Potassium was positively associated with pH, turbidity, Fe, Barytelphusa sp., Alitropus typus, Laccophilus sp., Notonecta sp., and Caenis sp., and negatively with magnesium, Culex larvae, Alitropus typus, and Notonecta sp. Iron (Fe) showed positive relationships with pH, turbidity, DO, nitrate,