Investigation of the effects of environmental variables on biodiversity pattern and seasonal distribution of macroinvertebrates in Shahrestanak River

Macroinvertebrates of running water are affected by their environment and their distribution in the habitat is affected by changes in environmental factors of the habitat. The aim of this study was to investigate the effect of some environmental factors on the large diversity of benthic invertebrates in Shahrestanak River, Karaj. Sampling of benthic invertebrates was conducted using a sorber sampler at six stations (with four replications per station) in 1397 and in two seasons of spring and autumn by measuring 10 environmental variables. A total of 12 families of large benthic invertebrates were identified in spring and 13 in autumn, in which the larvae of aquatic insects had the highest frequency. According to the results, station three (middle of the river) had the highest frequency and also the families Heptageniidae and Baetidae had a high frequency. In spring, the highest diversity, dominance and species richness was in station four (downstream) and the highest uniformity was in station six (downstream). The highest amount of diversity, dominance and uniformity in autumn was related to station one (upstream of the river) and the highest amount of species richness was related to station two (middle). Changes in environmental variables of resistance, electrical conductivity and total soluble solids (spring), flow rate and height (two seasons) were significantly different. In addition to the mentioned variables, the factors of width, depth, height and speed of water flow were among the factors affecting the frequency and composition of large species of benthic invertebrates. It seems that effective environmental factors in the study area have affected habitat conditions, diversity, abundance and species composition. Conducting these studies, while understanding the needs of aquatic organisms, contributes to effective conservation planning, determination of appropriate ecological water rights and sustainable abstraction of river resources.