Hydrobiological Study of Darjazin-River at Semnan Province

Hydrobiological Study of Darjazin-River at Semnan Province

Darjazin River is one of the freshwater rivers of Semnan province that during past years has been threatened by droughts and anthropogenic pollutions. This river supplies some parts of drinking water of mahdishahr city and some vicinity villages. The main aim of the present study is evaluation of benthose biodiversity of the river; for this purpose, hydrobiological studies of the river were carried out seasonally. At this study, four sampling stations were determined based on limnological methods along the river; afterwards sampling of invertebrates were performed seasonally during study period. The results showed that first station is free of pollution and has highest biodiversity while the second station is the most polluted region at the river because the first station has no pollutant source but the second station directly receives wastewater of rainbow trout fish culture center. Biological indices from Hydropsyche genus in first station and Simolium genus in second, third and fourth stations were observed. Species such as Rhitrogena sp., Liponeura sp. and Ecdyonurus sp. relate to free organic pollution area that in studied sampling stations were observed only in the first station only.