Iranian Scientific Fisheries Journal

fa مقاله علمی – پژوهشی:‌ بررسی کیفیت آب و وضعیت تروفیک (تغذیه ای) با تکیه بر شاخص‌های زیستی (پریفیتون و زئوپلانکتون) در رودخانه خرسان، استان چهارمحال و بختیاری Assessment of water quality and trophic status using biological indices (periphyton and zooplankton) in the Khersan River, Charmahal and Bakhtiari Province اكولوژي محيطهاي آبي اكولوژي محيطهاي آبي پژوهشي Research <div style="text-align: justify;">پژوهش حاضر با هدف بررسی کیفیت آب و وضعیت تروفیک(تغذیه ای) رودخانه خرسان در شهرستان لردگان (استان چهارمحال و بختیاری) انجام شد. برای ارزیابی شرایط زیستی، شاخص‌های Shannon (تنوع گونه)، Evenness (یکنواختی گونه)، Saprobic (آلودگی آلی) و TDI (شاخص تروفی دیاتومه) بر اساس جوامع پریفیتون و زئوپلانکتون مورد استفاده قرار گرفت. نمونه‌برداری به‌ صورت فصلی از پاییز 1402 لغایت تابستان 1403 در پنج ایستگاه انجام شد. نتایج نشان داد که در جوامع پریفیتونی پنج شاخه شامل 30 جنس و 38 گونه و در جوامع زئوپلانکتونی چهار شاخه شامل یک خانواده، 4 جنس و 13 گونه شناسایی شد. شاخه Bacillariophyta با 74 درصد و شاخه Rotifera با 56 درصد دارای بیشترین سهم گونه‌ای بودند. شاخص تنوع Shannon در بیشتر ایستگاه‌ها برای هر دو گروه زیستی در محدوده 1 الی 3 قرار گرفت که بیانگر شرایط آلودگی متوسط بود. شاخص یکنواختی گونه برای پریفیتون‌ها 97/0 -67/0و برای زئوپلانکتون‌ها 98/0 -44/0 محاسبه شد. شاخص Saproby بر اساس پریفیتون در محدوده 01/2-78/1 و بر اساس زئوپلانکتون در محدوده 01/2-51/1 قرار داشت. این نتایج نشان‌دهنده شرایط آلودگی آلی متوسط<a href="#_ftn1" name="_ftnref1" title="">[1]</a> در همه ایستگاه‌ها و فصول بود. شاخص دیاتومه نیز در محدوده 74/3-17/2 قرار گرفت که شرایط مزوتروفی تا یوتروفی را در بهار و تابستان و شرایط یوتروفی را در پاییز و زمستان نشان داد. این وضعیت بیانگر بارگذاری متوسط تا زیاد مواد مغذی در رودخانه است. بررسی‌ها نشان داد که با وجود غناء فصلی مواد مغذی به‌ویژه فسفر، محدودیت‌های فیزیکی (جریان شدید آب و مواد معلق)، مانع افزایش زی‌توده شدند. شاخهBacillariophyta  نه با تراکم بیشتر بلکه با مقاومت و رقابت مؤثر، غلبه داشتند. کنترل بارگذاری مواد مغذی برای حفظ تعادل توزیع گونه‌ها در آینده ضروری است. همچنین زئوپلانکتون‌های غالب در همه ایستگاه‌ها شاخصی از آلودگی آلی متوسط بودند که با نتایج پریفیتون‌ها هم‌خوانی داشت. <div>  <hr align="left" size="1" width="33%" > <div id="ftn1"><a href="#_ftnref1" name="_ftn1" title="">[1]</a> Beta-mesosaprobic</div> </div> </div> Introduction Hydrological processes and the physicochemical characteristics of rivers have been altered by climate change, particularly due to anthropogenic influences, resulting in significant consequences for riverine habitats and aquatic ecosystems (Gilvear et al., 2002).The combined effects of severe pollutant loading and disrupted hydrodynamics associated with dam construction further diminish the ecological capacity of river systems (Zhang et al., 2019). Advances in our understanding of the structural and functional dynamics of aquatic communities now provide opportunities for more effective management of environmental instability and pollution (Ekpo, 2013). Aquatic organisms, through their continuous interactions with one another and with the surrounding water environment, play a critical role in sustaining ecosystem integrity (Caroni et al., 2013). In flowing waters, where hydrological changes are rapid and difficult to estimate, physicochemical measurements due to their instantaneous nature cannot reflect the integration of multiple environmental factors or the long-term stability of river ecosystems. Consequently, biological monitoring, employing living organisms as bioindicators, is indispensable for assessing ecological conditions and detecting change (Oertel and Salanki, 2003). This study, conducted for the first time in the Khersan River basin, focuses on the Khersan 3 Dam, a double-arch concrete dam currently under construction in Lordegan County, Chaharmahal and Bakhtiari Province. In this study, biological Indices based on periphyton and zooplankton communities were used to assess the water quality status of the Marbareh and Bashar tributaries entering the Khersan River, in order to better understanding and implement necessary conservation strategies. Methodology Five stations were selected for investigation: St1: Marbareh River (under the entrance bridge of Ab-Malakh village); St2: Marbareh River (under the bridge of Narmeh village);St3: Upstream of the dam site (at the beginning of the reservoir); St4: Confluence of the Bashar and Marbareh rivers (before the village of Dowrah Ghamashkeh); St5: Location of the Khersan-3 Dam reservoir (the dam is under construction). Seasonal sampling was conducted throughout 2023 and 2024. Laboratory analyses of periphyton and zooplankton followed the protocols of APHA (2017), Wetzel and Linkens (1991), and Postel et al. (2000). Taxonomic identification was guided by references including Tiffany and Britton (1971), Habit and Pankow (1976), Hartley et al. (1996), Boltovskov (2000), Kuticova (1970), and Manolova (1964). Indices of species diversity and evenness were calculated according to Mason (1982). The saprobic index was computed following Sladechek (1973), Papadimitriou et al. (2010), and Li et al. (2017), while the Diatom Trophic Index was determined using the method of Kelly and Whitton (1995). Physicochemical parameters were measured in accordance with APHA (2017) standards. Statistical analyses were performed using SPSS version 22. Data were tested for normality, and non-normal distributions were normalized through logarithmic transformation. Temporal and spatial variations were examined using one-way ANOVA and Duncan’s post hoc test, and Pearson correlation was applied to explore relationships between selected physicochemical factors and biological indices. Results The annual qualitative and quantitative data analysis of microalgae in periphyton at sampling stations revealed the presence of 68 species. Periphyton organisms were identified across five phyla:Bacillariophyta,Cyanobacteria,Chlorophyta, Euglenozoa, and Xanthophyta. Bacillariophyta accounted for the highest percentage of species (74%). Dominant species were introduced at each station.Variance analysis comparing the mean total density of periphyton showed no significant differences between stations (p≥05/0).The lower densities occurred in warmer seasons and higher densities in colder seasons.The annual analysis of zooplankton at sampling stations revealed 13 species, 4 genera, and 1 family. Zooplankton were identified across four phyla: Rotifera, Ciliophora, Cladocera, and Copepoda. Rotifera accounted for the highest percentage of species (56%). Dominant species were introduced at each station. Duncan’s test in the comparative analysis of mean total density across stations identified Station 4 as significantly different (p≤05/0). zooplankton, also showed lower densities in warmer seasons and higher densities in colder seasons. Abiotic factors were measured to support biological data analysis and index values. Most stations, based on Shannon diversity index for both biological groups, fell within the range of 1 to 3, indicating moderate pollution. Species evenness index ranged: For periphyton: 0.67 to 0.97, For zooplankton: 0.44 to 0.98. Saprobic index based on periphyton ranged from 1.78 to 2.01, and for zooplankton from 1.51 to 2.01. The organic pollution index across all stations and seasons for both groups indicated β-mesosaprobic conditions, or moderate organic pollution. Diatom index values ranged from 2.17 to 3.74, indicating mesotrophic to eutrophic conditions in spring and summer, and eutrophic conditions in colder seasons suggesting moderate to high nutrient loading. <div aria-label="Page Break" class="cke_pagebreak" contenteditable="false" data-cke-display-name="pagebreak" data-cke-pagebreak="1" style="page-break-after:always" title="Page Break"></div>Discussion and conclusion The biological data from various stations along Khersan river during the 2023–2024 indicated  that the ecological conditions of these rivers generally fall within the range of moderate organic pollution. The Shannon species diversity index for both biological groups ranged between 1 and 3, corresponding to semi-stable conditions and moderate pollution levels.The saprobic index, calculated based on periphyton (1.78–2.01) and zooplankton (1.51–2.01), also placed all stations within the β-mesosaprobic range, indicating moderate organic pollution. The species evenness index showed relative balance, especially among periphyton, and species indicative of severe pollution were neither abundant nor dominant. The widespread presence of dominant diatoms such as Diatoma vulgaris and Navicula sp. both indicators of moderate pollution aligns with the saprobic index values. Similarly, the dominant zooplankton species across all stations were indicators of moderate organic pollution (Kulas et al., 2021). Station 4 exhibited the highest density of both periphyton and zooplankton communities, as well as the highest species diversity index for both groups. However, the lowest populations of these organisms were recorded in spring, likely due to flood conditions and high water discharge (50–66 m³/s) across all stations. The lowest Shannon diversity index values were also calculated for spring. The Shannon index for periphyton showed a strong inverse correlation with water flow (r = -0.67) and total suspended solids (TSS) (r=-0.59). The latter maybe affects light penetration, sediment abrasion, and substrate conditions (Yuli Herawati et al., 2024). The Shannon index for zooplankton showed a strong direct correlation with dissolved oxygen concentration (r = 0.5) and nitrate concentration (r = 0.53), and a strong inverse correlation with total phosphorus (r = -0.59). This may be influenced by the positive correlation (r=0.55) between phytoplankton and zooplankton diversity indices in the basin. In spring, floodwaters and wastewater inflows increased total phosphorus concentrations across all stations compared to colder seasons, while total nitrogen concentrations decreased in warmer seasons. This imbalance in the nitrogen-to-phosphorus ratio with high discharge and suspended solids, likely reduced light penetration resulting in lower diversity and density of periphyton, phytoplankton, and subsequently zooplankton (Liu et al., 2023). The saprobic index for periphyton showed a moderate direct correlation with BOD₅ (r = 0.45). Higher BOD₅ levels in winter, along with elevated saprobic index values, suggest increased organic pollution, altered nutrient cycles, and higher trophic levels (Sulastri et al., 2021). The Diatom Trophic Index (TDI), indicated eutrophic conditions with clear nutrient loading in autumn and winter, and mesotrophic to eutrophic conditions with moderate to critical nutrient loading in spring and summer.The dominance and species richness of Bacillariophyta (diatoms) in most stations (2–5) suggest favorable conditions for their high density compared to other microalgae like Cyanobacteria and Chlorophyta. Diatoms thrive in cold temperatures and turbid waters with high suspended solids, and their ability to attach to substrates and form biofilms helps them resist being washed away in high-flow environments (Yoo et al., 2025). The Khersan River basin represents a system with moderate to high nutrient loading. However, due to physical constraints such as strong water flow, turbidity, and high suspended solids, this nutrient richness does not translate into high biomass. Bacillariophyta dominate not by sheer density but through resilience and competitive advantage under harsh and variable conditions. Upstream activities, flow changes due to dam construction, and gradual inflow of runoff and organic pollutants may soon disrupt the relative balance of biological species distribution. This study is the first of its kind in this watershed, and future monitoring at shorter intervals is essential to assess nutrient loading and trophic status. Conflict of interest The authors declare that they have no conflict of interest. Acknowledgment We sincerely express our gratitude to the Iranian Fisheries Science Research Institute for its support, which provided the scientific and laboratory framework for this study. This research was derived from the project entitled “Investigation of the abundance and biodiversity of plankton and periphyton communities in the sub‑basin rivers of Khersan 3 Dam” with the approved code14-76-12-114-02049-021030. رودخانه خرسان, کیفیت آب, پریفیتون, زئوپلانکتون, شاخص زیستی Khersan River, water quality, Periphyton, Zooplankton, Biological Indecies 33 48 http://isfj.ir/browse.php?a_code=A-10-2501-2&slc_lang=fa&sid=1 Rahimeh Rahmati رحیمه رحمتی rahmati764@gmail.com 100319475328460041482 100319475328460041482 Yes Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Asieh Makhlough آسیه مخلوق asieh_makhlough@yahoo.com 100319475328460041483 100319475328460041483 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Narges Alishah نرگس عالیشاه n.alishah69@gmail.com 100319475328460041484 100319475328460041484 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Hasan Nasrolahzadeh Saravi حسن نصراله زاده ساروی hnsaravi@gmail.com 100319475328460041485 100319475328460041485 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Hasan Fazli حسن فضلی fazlihasan@gmail.com 100319475328460041486 100319475328460041486 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Behzad Rahnama بهزاد رهنما rahnama.behzad@gmail.com 100319475328460041487 100319475328460041487 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Ahad Ahmadnejad Chehreh احد احمدنژاد چهره Ahmadi.ahad@yahoo.com 100319475328460041488 100319475328460041488 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران Mohammad Kardar Rostami محمد کاردر رستمی MohammadKardarrostami@gmail.com 100319475328460041489 100319475328460041489 No Iranian Fisheries Science Research Institute (IFSRI) پژوهشکده اکولوژی دریای خزر، موسسه تحقیقات علوم شیلاتی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، ساری، ایران