Health assessment of Zarrin Gol River, Kaboudwal and Shirabad Streams in Golestan province using biological indices

The aim of this study was to evaluate the health of Kabudal and Shirabad Streams and Zarrin Gol River in Golestan Province using biological indices (benthic invertebrate community). Aquatic invertebrates are one of the most important and beneficial organisms in biological monitoring. In this study, based on the existing barriers and the possibility of access to the river, 5 stations in Kaboudwal Stream, 3 stations in Shirabad Stream and 10 stations in Zarrin Gol River were determined. In order to sample large benthic invertebrates using a surber sampler with dimensions of 30.5 30 30.5 cm and with 3 replications in each station seasonally in a period of one year (2018-2019) were collected and identified based on reliable identification keys. Then alpha, beta and multivariate biodiversity indices of water quality health assessment were studied. The results of this study showed that the effluent of fish farms had a significant effect on river water quality so that the percentage of pollution-sensitive families in the stations after fish farms decreased and increased the frequency of resistant families. The streams of Golestan province generally experience moderate ecological conditions and move towards poor conditions, which with the increasing trend of destruction of ecosystems along riparian zone and the impact of agricultural and aquaculture activities, it seems that we will have these conditions in the future.