Spatio-temporal variation in macro-invertebrate assemblage structure of kayar khola, Chitwan Nepal

Abstract

The spatial and temporal variations of the macro-invertebrate assemblages in rivers and streams of Nepal are poorly understood. The macro-invertebrate communities and their relationships with environmental variables were studied in Kayar Khola, Chitwan for one year (November 2020 to August 2021) covering four seasons. Each and every sampling station was visited once in each season. Macro-invertebrate sampling was conducted at each sampling station from 11 am to 2 pm by using a D-frame Net with a mesh size of 0.5mm. Altogether 42 Families belonging to 17 Orders, 5 Classes and 3 Phyla were found in present study. Among the collected macro-invertebrates, Hydropsychidae (20.20%) was recorded to be the most dominant family and followed by Thiaridae (15.76%), Heptageniidae (12.02%), Baetidae (9.43%), and Psephenidae (5.09%) respectively. Family Viviparidae (0.05%) was less dominant and found only in the spring season at site C of Kayar Khola. The Order Trichoptera was found to be the most dominant order with 408 individuals. The highest Shannon-Weiner diversity index (2.39) was observed during winter season whereas the lowest value (1.61) observed in summer season. Maximum family richness value (21.0) was found in winter season and the minimum (7.75) found in summer season. The correspondence analysis (CCA) reveals a significant correlation between macro-invertebrate assemblage and environmental variables. Cluster analysis depicts that similarity between macroinvertebrates decreases as the distance of sites increases.