Spatio-Temporal Variation in Macro Invertebrates of Ghodaghodi lake Far-west Kailali Nepal

Abstract

Recently species associated with fresh water ecosystems have steeply declined due to pollution, over exploitation, habitat modification, environmental degradation and impact of other developmental activities. The physio-chemical parameters are also changing in these recent years which are also the cause for the loss in aquatic diversity. Macro-invertebrates forms important links in food chain and are considered as an indicator of changes in aquatic habitat. Since Ghodaghodi Lake contributes habitat for wide variety of aquatic species, the status of macro-invertebrates is yet to be known. Therefore, this study was designed to investigate the spatio-temporal variations of macro-invertebrates and describe the relationship between certain environmental variables and assemblage structure of macro invertebrates. Macro-invertebrates samples were collected in seasonal basis from four sites of

the Lake by using

bin sampler and then analyzed. Macro-invertebrate community richness, Shannon-Wiener diversity, and evenness were calculated for each site.Data on the temperature, depth, pH, conductivity, dissolved oxygen, hardness, free carbon dioxide, alkalinity and total dissolved solid was recorded.Redundancy analysis (RDA) was performed to examine the relationship between the Macro-invertebrate assemblages and environmental variables.Altogether 42families belonging 18 orders, 6 classes and3 phylum’s of macro invertebrates were recorded during the study period. The highest diversity index value (3.16)

was observed

in winter season and lowest value (3.03) was observed in the autumn season. The highest diversity index value (3.22) was observed at site C and lowest value (3.10) was observed at site B. Culicidae family (9.84%)had highest frequency in all four season and four station.The Scolopendridae (0.22%) and Sphaeriidae (0.22%) familieshad lowest frequency. The water temperature was found to be highest at site D at summer season i.e., 30.2 °C. Depth of sampling sites of Lake was highest at site D in summer season i.e., 300 cm. TDS was maximum at site C in autumn season i.e., 196.1. Conductivity was recorded maximum at site A in summer season i.e., 236.5 µs. The pH of the water was alkaline throughout the year i.e., greater than 7 pH. It was recorded 7.1-8.5. The maximum DO was found to be 5.7 mg/l at site A in winter season. The free CO2 was 3.6 mg/l highest at site B in winter season. Hardness was found to be highest at site A in summer season i.e., 379 mg/l. The alkalinity of the water was found to be maximum at site C in winter season i.e., 228 mg/l. Redundancy Analysis (RDA) shows that: Family Culicidae, lycosidae, Thiardae were most strongly positively correlated with the temperature in summer season and strongly negatively correlated with alkalinity in autumn and winter season.Noteridae, Bulinidae, Achatinidae, Lumbricidae, Ephydridae, Hydrometridae are positively correlated with DO, depth, conductivity and hardness of water. Mutillidae, Curculionidae, Lymnaeoidae, Notonectidae, Scolopendridae, Pyralidae, Elmidae, Viviparidae, Corduliidae, Gerridaepreferred positively correlated with pH, total dissolved solid and CO2 . Seasonal variation and location influence the macro-invertebrates communities