Hydrobiological Study of Darjazin-River at Semnan Province

mainly due to the fact that the biota are continuous witnesses of the river s state of health and are collectively sensitive to the whole range of potential pollutants [4]. Monitoring programs for freshwater ecosystems have increasingly used benthic invertebrate communities as an indicator of environmental pollution to complement chemical, microbiological and toxicity testing of surface waters [5-6]. Resident biota (e.g., benthic invertebrates, fish and periphyton) in a water body are natural monitors of environmental quality and can reveal the effects of episodic and cumulative pollution and habitat alteration [7]. Biological surveys and assessments are the primary approaches to biomonitoring. Water pollution and shortage of clean water reservoirs is one of the most urgent problems of our times. One of the most common contaminations is the organic pollutants, which can originate from many different sources [8]. The usual situation is the measurement of multiple parameters, taken at different monitoring times, and from many monitoring stations [9]. The main objective of the present study was evaluation of Darjazin River in point of hydrobiological and limnological views.

Keywords:

Semnan , Biological index , Darjazin river , Limnological method , Benthose