The Effect of Drought on the Diversity and Frequency of Benthic Macroinvertebrates: A Case Study of Zayandeh Rud River, Isfahan, Iran

For investigating the effect of drought on Benthic macroinvertebrates communities in Zayande-Roud River, presence and abundance of macroinvertebrates were compared in spring and summer of 2007 and 2013 in 5 stations. To this purpose, 5 stations were selected and monthly sampled when the river was flowing in 2013. Sampling was done in tree replicates by Sourber sampler (area 625 cm2) and PVC tube with 90 mm diameter in 3 iterations. The macroinvertebrates samples were identified and counted in laboratory. After spotting taxonomic composition and investigating some population parameters, the results were compared with the data obtained in 2007. According to the results, 19 families of macroinvertebrates were identified. The results also showed that Corixidae, Hydrobiidae and Haplotaxidae families observed in August and July 2013 were not reported in the same period in 2007. However, Elmidae, Athericidae, Erpobdellidae and Valvatidae families reported in 2007were not observed in 2013. In addition, the results of the Paired-Sample T-Test showed a significant reduction in benthic macroinvertebrate's density in comparison with the results obtained in 2007 (p<0.05). Moreover, in some stations Shannon-Wiener, Brillouin and EPT indices showed a severe reduction in density and frequency which effected by drought.