Biodiversity Study and the Effect of Some Environmental Factors on Distribution of Macrobenthos in Jajrood and Karaj Rivers

In this study, the identification and biodiversity of macrobenthos of Jajrood and Karaj protected rivers which provide a large portion of Tehran's drinking water, have been studied simultaneously for three consecutive years. Physicochemical and macrobenthos samples were collected with three replications, during three consecutive years from 19 stations with a Surber sampler. Statistical analyses were done by SPSS, Past and R softwares. In Jajrood River, 6667 macrobenthos in 22 families and in Karaj River, 13,246 macrobenthos in 24 families were identified respectively .The highest abundance and diversity of macrobenthos and the most appropriate time for sampling was in summer. The results of CCA showed that physicochemical parameters TSS, EC , DO and pH had the highest effect on the distribution of macrobenthos. In Jajrood River, Baetide and in Karaj River Simullidae are the most dominant families. The Simpson dominance index in both rivers tends to one and indicating the high frequency of one or more families compared to the others. The mean values ​​of Shannon-Wiener (H) index varied in the four sampling periods in Karaj River between 2.04± 0.11 to 2.5 ± 0.06 and in Jajrood River between 1.4 ± 0.22 to 2.4± 0.42. Both Rivers are similar in terms of macrobenthos fauna and biodiversity. Results of biodiversity indices showed that human activities affect macrobenthos communities and the most negative effect on the ecosystem of the two rivers is due to tourism activities, Recreational use and land use changes.