Iranian Scientific Fisheries Journal

fa مقاله علمی – پژوهشی:‌ پایش میکروبی منابع آب سطحی در حوضه آبریز سرشاخه‌های رودخانه سیروان (سنندج) طی سال‌های 1403-1402 Microbial monitoring of surface water resources in the Sirvan River tributary catchment basin (Sanandaj) during 2023-2024 آلودگي محيطهاي آبي آلودگي محيطهاي آبي پژوهشي Research پایش میکروبی منابع آب سطحی به‌ویژه در نواحی حساس مانند حوضه‌های آبریز سدها، نقش حیاتی در حفظ سلامت عمومی و پایداری اکوسیستم‌های آبی ایفاء می‌کند. این مطالعه با هدف بررسی وضعیت آلودگی میکروبی در حوضه آبریز رودخانه سیروان در استان کردستان طی سال‌های آبی 1403-1402 انجام شد. نمونه‌برداری‌ها به ‌صورت ماهانه و با رعایت شرایط استریل از شش ایستگاه منتخب شامل ایستگاه 1 (بالادست قشلاق، زیر پل)، ایستگاه 2 (شاخه قشلاق رود قبل از تصفیه خانه)، ایستگاه 3 (شاخه قشلاق رود، پایین دست تصفیه خانه)، ایستگاه 4 (شاخه قشلاق رود، حدود 3 کیلومتر پایین‌تر از ایستگاه 2)، ایستگاه 5 (شاخه گاوه رود) و ایستگاه 6 (شاخه سیروان، پشت سد) انجام گرفت. شاخص‌های میکروبی شامل شمارش کل باکتری‌ها، کلیفرم‌های کل، کلیفرم‌های مدفوعی و  Escherichia coliبا استفاده از محیط‌های کشت پلیت کانت آگار و ECC کروم آگار مطابق با استاندارد APHA  (2017) اندازه‌گیری شدند. نتایج نشان داد که بار میکروبی در ایستگاه‌ها تفاوت معنی‌داری دارد (05/0p≤) به‌طوری‌که ایستگاه ۴، واقع در پایین‌دست تصفیه‌خانه، دارای بیشترین میزان آلودگی بود و در ماه آبان غلظت کلیفرم‌های کل تا ۷۰۰۰۰۰ واحد تشکیل‌دهنده کلنی در 100 میلی‌‌لیتر ثبت شد. در مقابل، ایستگاه ۵ واقع در منطقه‌ای با کمترین فعالیت انسانی، دارای کمترین بار میکروبی بود. تحلیل فصلی داده‌ها نیز بیانگر افزایش قابل‌ملاحظه شاخص‌های آلودگی در فصل تابستان به‌ویژه در ایستگاه‌های مجاور فعالیت‌های انسانی و کشاورزی بود. یافته‌های این تحقیق نشان‌دهنده نقش مؤثر فاضلاب‌های انسانی، رواناب‌های کشاورزی و ناکارآمدی سیستم‌های تصفیه در کاهش کیفیت بهداشتی منابع آب سطحی منطقه است. با توجه به اهمیت رودخانه سیروان در تأمین آب شرب و کشاورزی استان کردستان، نتایج این مطالعه می‌تواند مبنایی برای شناسایی نقاط بحرانی، اصلاح زیرساخت‌های تصفیه و تدوین برنامه‌های پایش و مدیریت مستمر کیفیت آب سطحی در سطح حوضه آبریز باشد. Introduction <h3 style="text-align:justify">The Sirvan River is a vital freshwater source in Kurdistan Province, flowing through both urban and rural landscapes. Its proximity to human settlements, agricultural zones, and livestock operations increases the risk of contamination from untreated wastewater and surface runoff. Consequently, microbial monitoring of surface water within this watershed is essential for evaluating the region’s sanitary and environmental conditions. Microorganisms in aquatic ecosystems, beyond their ecological functions, are widely recognized as reliable indicators of water quality. Fluctuations in microbial populations often signal the presence of pollutants such as domestic sewage, animal waste, and nutrient compounds (Bradshaw et al., 2016). Among these indicators, coliform bacteria particularly fecal coliforms and Escherichia coli are of critical importance due to their intestinal origin and thermotolerance, making them precise markers of contamination from human and animal sources (Aenab and Singh, 2015). Numerous international studies have explored the factors influencing the presence and distribution of indicator bacteria in surface waters. For example, Pall et al. (2013) and Islam et al. (2017) examined the roles of temperature, precipitation, land use, and wastewater treatment efficiency in microbial load variation. Newton and McMahon (2011) investigated the relationship between organic and inorganic compounds and microbial community structure in lakes. At the watershed scale, Flood et al. (2022) highlighted the influence of geological and hydrological features on microbial contamination in rivers. Similarly, Park et al. (2021) demonstrated the impact of vegetation cover and land slope on bacterial distribution in South Korea. In Iran, several studies have addressed microbial water quality. Roshani-Sefidkouhi et al. (2025) assessed the Chahnimeh reservoirs in Sistan and Baluchestan Province, while Khatib Haghighi and Ghaani (2018) evaluated urban and rural drinking water sources in Gilan Province using total and fecal coliform indicators. However, most of these investigations were limited to cross-sectional designs or specific seasons. Comprehensive studies on spatial and seasonal variations of microbial indicators in Iranian rivers particularly the Sirvan River remain scarce. This study presents a year-long monitoring of microbial indicators, including total coliforms, fecal coliforms, and E. coli, across six stations in the Sirvan River watershed, covering a full hydrological cycle (July 2023 to June 2024). By analyzing seasonal and spatial trends and examining the influence of surrounding human activities, this research offers a novel approach to surface water quality assessment. The findings aim to identify pollution hotspots, evaluate sanitary conditions, and inform water quality management strategies for Kurdistan Province and similar regions.</h3> Results Microbial contamination in the Sirvan River watershed was assessed by quantifying total bacteria, total coliforms, fecal coliforms, and E. coli across multiple stations and seasons during 2023–2024. Maximum recorded values were 1×10⁸ CFU/100 ml for total bacteria, 7×10⁵ for total coliforms, 4.2×10⁵ for fecal coliforms, and 3.7×10⁵ for E. coli. The highest total bacterial count occurred at Station 2 in November 2023, while peak coliform and E. coli levels were observed at Station 4 in January 2024. Seasonal analysis revealed that bacterial concentrations peaked in summer (6.56 ± 0.32 log CFU/100 ml) and were lowest in winter (5.55 ± 0.87 log CFU/100 ml). Spatially, Station 3 consistently exhibited the highest bacterial load, while Station 2 had the lowest. Statistically significant differences were found between winter and other seasons (p≤0.05), as well as among stations (p≤0.05). Total coliforms followed a similar seasonal pattern, with highest mean counts in summer (4.87±0.77 log CFU/100 ml), followed by autumn (4.27±0.95), spring (3.86±0.50), and winter (3.12±1.91). Stations 3 and 4 were the most contaminated, while Stations 1 and 5 consistently showed the lowest levels. Seasonal variation in total coliforms was statistically significant (p≤0.05), with summer values markedly higher than winter. Fecal coliforms also peaked in summer (3.23±1.72 log CFU/100 ml) and were lowest in winter (2.72±1.72). Station 4 recorded the highest levels, significantly differing from other stations (p≤0.05), while Stations 1 and 5 had the lowest. However, seasonal differences in fecal coliforms were not statistically significant. E. coli concentrations were highest in summer (3.09±1.58 log CFU/100 ml) and lowest in winter (2.97±1.51). Stations 3 and 4 again showed the highest contamination, with statistically significant differences compared to other stations (p≤0.05). Stations 1 and 5 did not show significant contamination levels. Seasonal variation in E. coli density was not statistically significant. Overall, the data revealed pronounced spatial heterogeneity in microbial contamination, with consistently elevated levels at Stations 3 and 4 areas characterized by intensive human and agricultural activity. Seasonal effects, particularly during summer and autumn, were major contributors to increased bacterial loads due to higher temperatures and runoff. These findings underscore the need for targeted pollution control measures in identified hotspots within the Sirvan River catchment. <h3 style="text-align:justify">Discussion and conclusion  </h3> <h3 style="text-align:justify">The elevated bacterial concentrations observed in downstream stations (2, 3, and 4) of the Sirvan River reflect the impact of human activities, including the discharge of untreated or partially treated sewage and agricultural runoff (Helmer and Hespanhol, 1997; Agarwal and Rajwar, 2010; Aenab and Singh, 2015). These conditions are exacerbated by warm water temperatures, reduced flow rates, increased evaporation, and higher pollutant loads factors consistent with microbial contamination patterns in similar ecosystems (Rusiñol et al., 2020; Rather et al., 2023; Al-Afify et al., 2023). The presence of E. coli in elevated concentrations is a clear indicator of fecal contamination and poses serious health risks to communities near the river. The findings highlight the inadequacy of existing wastewater treatment systems and the urgent need for infrastructure upgrades to mitigate pollution. Lower bacterial concentrations at upstream sites suggest the effectiveness of natural filtration by vegetation, topographical separation from pollution sources, and hydrological buffering (Yaghoubzadeh and Safari, 2016; Wang et al., 2022). This study reinforces the importance of regular microbial water quality monitoring in the Sirvan River watershed using robust indicators such as E. coli. Effective management requires prioritizing the identification and control of both point and non-point source pollution, especially during peak contamination seasons. Strategies should include improved wastewater treatment, public awareness campaigns, and ecological restoration of water bodies. Integrated watershed management, supported by collaboration among water, health, and environmental authorities, is essential for safeguarding water quality and public health.</h3> <h3 style="text-align:justify">Conflict of interest</h3> The authors declare that they have no conflict of interest Acknowledgment We hereby sincerely thank the Caspian Sea Ecology Research Center and Iranian Fisheries Science Research Institute for providing the scientific and laboratory basis for this research. پایش میکروبی, کلیفرم مدفوعی, Escherichia coli, رودخانه سیروان, کیفیت آب Microbial monitoring, fecal coliform, Escherichia coli, Sirvan River, water quality 69 81 http://isfj.ir/browse.php?a_code=A-10-1386-13&slc_lang=fa&sid=1 zahra yaghoubzadeh زهرا یعقوب زاده za_yaghoub@yahoo.com 100319475328460040964 100319475328460040964 Yes Agricultural Research, Education and Extension Organization پژوهشکده اکولوژی دریای خزر، مؤسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Faezeh Turk Pahnabi فائزه ترک پهنابی pahnabifaezeh@gmail.com 100319475328460040965 100319475328460040965 No Agricultural Research, Education and Extension Organization پژوهشکده اکولوژی دریای خزر، مؤسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران