شناسايي و بررسي تنوع ماكروبنتوز هاي رودخانه كرج

Identify and evaluate the diversity of Macrobenthos in Karaj River

مطالعه مشتمل بر شناسايي و پراكندگي ماكروبنتوزها در رودخانه كرج مي باشد، بررسي مذكور از مهر سال 1393 شروع و در تير سال 1394 پايان يافت. در منطقه مورد بررسي، پنج ايستگاه مطالعاتي براساس شرايط تاثيرگذاري محيطي انتخاب و فون ماكروبنتوزهاي آن با تواتر فصلي توسط كوادرات با ابعاد50×50 سانتي متر و با 5 تكرار در هر ايستگاه نمونه برداري شد. نمونه ها توسط فرمالين 4% تثبيت و در آزمايشگاه جداسازي، شناسايي و شمارش گرديدند. در بررسي هاي انجام شده ،24 جنس از 22 خانواده و 6 رده ماكروبنتوز شناسايي گرديدند، با بيشترين فراواني در فصل زمستان و كمترين فراواني در فصل بهار. از ميان پنج ايستگاه تعيين شده، ايستگاه 4 در فصل زمستان با 1067 عدد در متر مربع بيشترين فراواني و ايستگاه 5 در فصل بهار با 254 عدد در متر مربع كمترين فراواني را دارا بودند. در ميان نمونه هاي شناسايي شده ،رده Insecta با 88.7% فراواني بيشترين تعداد و رده Malacostraca با 0.1% ازكمترين فراواني برخوردار بودند. از ميان نمونه هاي شناسايي شده،گونه Simulium sp. با فراواني 879 عدد در متر مربع بيشترين تعداد و گونه هاي Asellus aquaticus ، Atherix sp. با فراواني 1 عدد در متر مربع كمترين تعداد را داشتند.در طي اين مطالعه ميانگين شاخص تنوع گونه اي شانون وينر1.73، غالبيت گونه اي سيمپسون 0.74 و غناي گونه اي مارگالف 3.31 محاسبه شد. براساس مقادير شاخص زيستي «HFBI»، كيفيت آب ايستگاه هاي منتخب، در 3 طبقه كيفي عالي ، خيلي خوب و خوب ارزيابي شدند.

Karaj River as one of the most important water sources of Tehran city, has special importance. This study consisted of diversity and distribution of Macrobenthos on Karaj River that was conducted during years 2014-2015. It was started in fall 2014 and it was finished in summer 2015. In the mentioned area, the total of five study stations were selected based on environmental impact, Macrobenthos fauna samples were taken by Quadrat with dimensions of 50 × 50 cm such that were repeated 5 times at each station with seasonal frequency. Samples were fixed with 4% formalin, were separated in a lab, and then identified and counted. In surveys conducted, 23 genuses from 21 families and 5 orders of Macrobenthos were identified. The results show the station 4 in winter season had most abundance (1067) and the station 5 in spring season had the less abundance (254) of specimen. Insecta had the most abundance (88.8 % of total) and Malacostraca had the less abundance (0.1 % of total) between five classes were identified on Karaj River. The genera of the Simulim with the number of 879 per square meter the highest abundance and The genuses of the Asellus and Atherix With the number of 1 per square meter the lowest among the species had been identified. During this study the average of the Shannon-Wiener diversity index was calculated 1.73, Simpson dominance species was calculated 0.74 and Margalef richness species was calculated 3.31. According to the biological values of Hilsenhoff (HFBI), the water quality status of Karaj River at stations 2 and 3 were evaluated excellent, at stations 5 was evaluated very well and at stations 1 and 4 were evaluated well. Overall according to the results, it was determined that aquatic insects constitute the dominant population of the benthic fauna in Karaj River. In winter season the classes: Insecta, Turbellaria, Gastropoda, Malacostraca and Clitellata had the greatest density and diversity compared to other seasons.