Quick Assessment of Gorganrood River Water Quality Based on Biotic Indices

Pollutants have various direct and indirect adverse impacts on the environment, including water quality changes as well as changes in benthic organisms distribution. Therefore, the quality of water can be assessed by sampling aquatic environments and their benthoses .Studying and assessing the structure of benthic communities in aquatic ecosystems have a remarkable role in the ecological assessments of the aquatic organisms. The importance of benthoses is not only because of their existence in the food chain, but also because of existence or non-existence of some of benthic species which can show the quality of water in terms of the amount of pollution or nonpollution .Gorganrood is situated in Golestan state. It oriinates from Golidagh highlands in Golestan National Park and then after crossing Gonbadkavoos and AghGhala located in the west of KhajehNafas,it enters the Caspian Sea. Due to flood breaking out in the rainy months of the year causing severe turbidity ,as well as the high flow rate of Gorganrood river, the density of the benthoses is less than the other rivers .Among various macrobenthoses ,14 families have been recognized whose highest densities belong to Diptera (Chironomidae) and Oligochaeta (Tubifix). One of the reasons of species enrichment reduction and the density and the abundance of macrobenthoses in the above-mentioned river is the lack of appropriate vegetal coverage along the river. Pollutants, and sewages resulting from human and natural pollutions due to the improvement of country industries and establishing several factories along the river and their water consumption along with releasing sewages to the river without filtration can cause significant danger for the aquatic organisms. Due to high flow rate and turbidity seen in the upper parts of the river, the amount of benthic organisms shows less density. Upstream stations are more influenced with water features. The water of the river is polluted while flowing and mixing with urban and rural sewages, particularly Gonbad sewages .The amount of such pollution is various based on different flow rate of water. The station lacks natural water flow in summers and only a stream of urban and rural sewages can be seen. The results achieved from Saprobic and Hilsenhoff methods with physical parameters show such a problem.