Study of correlation between macrofauna population and water quality status, of Karaj River

The distribution, abundance and assemblage structure of macrofauna as one of the important tools in assessing the quality of water, were determined during 9 stations in Karaj River, seasonally; 2017-2018. Sampling of macrofauna was performed with Surber sampler. Also, depth (11±3 cm), temperature (10.5 ± 4.3 ◦C), Salinity (0.01±0.01 ppt), DO (9.3±0.9 mg/l), EC (0.19±0.1ᵘs/m), pH (8.5±0.2), TDS (0.12±0.07 g/l) and Turbidity (19.6±29.1NTU) were measured in each station by multimeter device. A total 38454 individuals belonged to 42 families and 52 taxa were identified. Chironomidae was the most dominant family. The nine families making up 83% of all specimens (Baetis, Tubifex, Micrasema, Rhithrogena, Eporus, Hydropsyche, Leptophlebiidae and Simulium). The maximum density (7758 ind/m2) was obtained at station 8 while the minimum (592 ind/m2) was observed at station 5. The station 7 was characterized by the higher species diversity (H', 2.78) and the stations 8 was characterized by the lowest diversity indices (H', 1.57). The PCA showed that TDS, EC, Salinity and pH were the main parameters, and the cluster analysis divided the stations into three groups (G1: St2, St 6; G2: St 8, St 9, St 1, St 7; G3: St 4, St 5, St 3). Although the Shannon Index evaluated the upstream stations better, it generally assessed the water quality of the Karaj River as medium.