The effect of environmental factors on the distribution and abundance of benthic macroinvertebrates in Chehel Chai River in Golestan province

Some macroinvertebrates have been identified as bio-indicators indices of stream health and are as the most useful and efficacious. The purpose of this study was to investigate the macroinvertebrate communities and their relationship with environmental factors in the Chehel Chai River of Minoodasht, Golestan province. The study of the abundance and distribution of macroinvertebrate in 2017 seasonally at 5 stations in upstream, forest, tourism area، agricultural and urban areas was performed with 3 replications using Surber sampler (0.09 m2). In this study ،in total fauna including 2 phyllum, 2 class, 4 order and 10 families were identified. The most frequent species were Ephemeroptera and Baetidae. The highest species abundance and the lowest species abundance were observed in winter and in spring, respectively. The highest Hilsenhoff index recorded in summer in urban area (7.19) and the lowest in autumn in upstream area (4.06). The Results from the mean HFBI index 5.44 showed Chehel Tea River with organic pollution class of water quality resulting that an increase in organic matter in the downstream stations due to agricultural activities in this area, release of urban wastewater and tourism affairs. Increase of pollution resistant species such as Tubificidae and Chironomidae families, indicated low water quality in this area.