BMWP and ASPT biotic indices, useful tools to monitor stream water quality: Case study Ghale Rudkhan River, Guilan, Iran

Biotic index Benthic macroinvertebrates BMWP/ASPT Water quality

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December 25, 2024

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The objectives of the present study were to evaluate the health status and extent of pollution in Ghale Rudkhan River using the biotic index BMWP/ASPT, Margalef species richness, and Simpson and Jaccard similarity indices. Five sampling sites were selected from upstream to downstream reach of the river, and the samples were collected in each site using a Surber sampler (900 cm2 area). In total, 5134 individuals of macroinvertebrates were enumerated and identified, belonging to 35 species and 30 families, 10 orders, 4 classes, and 3 phyla. Orders of Diptera, Ephemeroptera, Trichoptera, and Plecoptera were the most dominant taxa, respectively. Site 1, located at the upstream reach of the river, exhibited better quality indexes. In contrast, site 5, located at the downstream reach, had the poorest water quality due to relatively high loads of pollutants from the river's upper reaches and domestic and agricultural wastes. The mean±SD of the evaluated indexes were: BMWP/ASPT as 5.78±1.09, Margalef index as 1.38±0.48, Simpson index as 0.56±0.16 and Jaccard and 0.48±0.08. According to the BWMP/ASPT index, the Ghale Rudkhan River is classified into three classes of pollution: clean water at sites 1 and 2 (with values of 6.02 and 6.65), slightly polluted water at sites 3 and 4 (with values of 5.63 and 5.68) and moderately polluted at sites 5 (with value of 4.96).