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Biological and saprobic evaluation of Tajan River using benthic macroinvertebrates
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Faeze Delbari   , Kamran Rezaei tavabe * , Alireza Mirvaghefi , Erfan Salmroodi , Ahmad Reza Lahijanzade , Masoud Bagherzade Karimi |
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Abstract: (862 Views) |
Introduction: Tajan River with a length of about 120km located in Mazandaran province originates from the heights of Alborz and leads to the Caspian Sea.
Materials & Methods: According to the limnological conditions of the river and the establishment of polluting sources on the banks of the river, 9 study stations were selected in two seasons, winter and summer (January 2021 and June 2021), and using a Sorber device, sampling of large benthic invertebrates was carried out. In addition to biological sampling, water samples were taken to investigate the relationship of some physicochemical parameters such as: temperature, ORP, EC, TSS, TDS and DO with the fluctuations of HFBI macrobenthic communities. Physicochemical factors were analyzed at the sampling site using portable devices.
Results: After identifying and counting benthic samples from the studied stations, water pollution and biological index Z were evaluated using Bohr's formula and according to the Hilsenhof table. Based on the results, the values of DO and ORP decreased from the upstream to the downstream of the river, and on the contrary, the values of temperature, EC, TSS and TDS increased, which is due to the increase in agricultural activities and the entry of urban and industrial pollutants into the downstream of the Tajan river. In this study, the highest frequency was related to species from the orders of Ephemeroptera, Trichoptera and Bosommatophora. The saprobic conditions of the river went from upstream to downstream in the cold season to polysaprobic and in the warm season, fluctuations were observed among the stations.
Conclusion: In general, considering the Z index, in the cold season in the upstream stations due to the mountainous nature and lack of human interference, the water has a better quality and the indicator species of the oligotrophic waters were dominant. In the downstream stations in the cold season and also in all the stations in the hot season, due to the presence of various pollutants and temperature changes, pollution-resistant species prevailed in the stations. According to the Hilsenhof Biological Index (HFBI), the water quality status of Tajen River was assessed as good to relatively poor in the cold season and poor to very poor in the hot season. |
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| Keywords: Physicochemical parameters, Hilsenhof index, Benthic invertebrates, Pollution, Z index |
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Full-Text [PDF 1039 kb]
(363 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2025/09/7 | Accepted: 2025/10/2 | Published: 2025/10/2
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