Bardukh Gabrielyan

High-altitude freshwater ecosystems are particularly vulnerable to anthropogenic impacts, yet spatial and seasonal variations in biological responses remain poorly understood. This study assessed the health status of narrow-clawed crayfish (Pontastacus leptodactylus) and habitat condition in two hydrologically and environmentally distinct bays of Lake Sevan, Armenia, using an integrated hydrochemical and multibiomarker approach. Water quality and crayfish populations were measured in Lichk and Lchashen Bays in May, July, and October 2024 and 2025. In total, 120 crayfish specimens were examined, and oxidative stress responses were assessed in the hepatopancreas, gills, and muscle using MDA, GSH, GST, KAT, and SOD. Lchashen Bay experienced more adverse environmental conditions, characterized by pronounced hypoxia in the summer (3.4–3.9 mg O₂ L⁻¹), higher biochemical oxygen demand and permanganate oxidation, and elevated K, Na, and Mg concentrations. Biomarker responses showed significant seasonal variation, typically with highest values in July. Crayfish from Lchashen Bay consistently demonstrated higher biomarker responses than crayfish from Lichk Bay across all tissues and sampling periods. Integrated biomarker response (IBR) values confirmed this spatial pattern, indicating greater physiological stress in Lchashen Bay. The combined hydrochemical and biomarker approach demonstrates the suitability of P. leptodactylus as an indicator species for assessing sublethal environmental stress in Lake Sevan.

The quality of riverine water is largely influenced by anthropogenic activity; however, worldwide monitoring practices remain largely limited to assessing water physicochemical parameters. To evaluate the potential of river contaminants to cause biological effects, two standard tests with the Tradescantia plant were used: Trad-SHM (stamen hair mutations) and Trad-MN (appearance of micronuclei in sporogenic cells). Water samples were collected from nine localities along the two rivers of the Kura basin: before and after the towns of Spitak, Vanadzor, Tumanyan, Alaverdi, and before Akhtala. The sampling locations were impacted by different anthropogenic sources—domestic and agricultural (Spitak and Vanadzor) and domestic and mining (Tumanyan, Alaverdi, and Akhtala). The biological responses were compared to water quality monitoring data based on physicochemical parameters (ions and metals). Monitoring results indicated “good” or “average” water quality, except for the exceedance of Fe, Mn, Cu, and Pb concentrations in the mining-affected areas. However, Tradescantia showed significantly increased frequency of hair cell mutations and micronucleus formation from urban/agricultural to mining-affected samples. The multivariate PCA analysis distinguished between the samples by associating ammonium and nitrate levels with the samples from urban/agricultural areas and the concentrations of Fe, Mn, Co, and Al with the biological responses in mining-affected samples. However, most likely, toxic substances in the riverine waters acted synergistically. The results indicated that compliance with chemical standards does not necessarily equate to biological safety. They emphasize the need to incorporate biological effects into monitoring programs to improve their contribution to informed decision-making regarding environmental impacts.

Freshwater ecosystems are increasingly affected by anthropogenic stressors, necessitating the assessment of sensitive biomarkers of sublethal impact. This study assessed the seasonal variability of oxidative stress parameters in the amphipod Gammarus lacustris from three tributaries of Lake Sevan (Armenia)—the Gavaraget, Karchagbyur, and Argichi Rivers—with contrasting hydrophysical and hydrochemical conditions. During 2022–2024, lipid peroxidation (MDA), antioxidant enzymes (CAT, SOD, GR, and GST), and glutathione (GSH) were measured in specimens collected in May, July, and October and related to temperature, dissolved oxygen, nutrients, major ions, and trace elements. Biomarker levels generally increased from spring to summer and declined in autumn, following temperature and photoperiod patterns. Statistically significant seasonal dynamics were most consistent in the Karchaghbyur River, while, in the Gavaraget and Argichi Rivers, they varied by biomarker and year. Amphipods from the Gavaraget River exhibited consistently elevated levels of oxidative stress biomarkers, consistent with elevated nutrient concentrations and stronger anthropogenic impacts. A short-term increase in all biomarkers in the Argichi River in 2023 indicated episodic acute stress. Overall, the response of oxidative stress biomarkers in G. lacustris reflected both the natural seasonal variability and spatial differences in environmental pressure, confirming their potential as a tool for monitoring Lake Sevan’s tributaries.

Fish morphological traits are increasingly recognized as sensitive bioindicators of aquatic ecosystem quality. This study investigated the associations between dominant meristic traits, which are a subset of morphological features of six common freshwater species, Alburnus alburnus, Perca fluviatilis, Abramis brama, Rutilus rutilus, Scardinius erythrophthalmus, and Carassius carassius, and chemical parameters of water in the regulated ecosystem of the Styr River, Ukraine. Water quality was evaluated using biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), dissolved oxygen (DO), nutrients, solids, pH, and water quality classes (WQC). Meristic traits of fish were analyzed through frequency analysis of species (FAS) and the Zakharov scoring method (ZSM), while hierarchical cluster analysis (HCA) and neural networks (NN) were applied to detect associations between meristic traits of fish and water chemical parameters. Results revealed that overall water quality corresponded to WQC I–II (clean to moderately polluted), although COD consistently exceeded permissible limits. Key meristic traits, including fin rays, scales, and gill rakers, showed significant sensitivity to environmental variability, with species-specific responses reflecting ecological adaptation. The integrative use of WQC, FAS, ZSM, HCA, and NN demonstrated the potential of meristic traits to serve as reliable indicators of ecological integrity in freshwater systems.

Приведены данные исследований видового состава гельминтофауны и степени инвазированности рыб нижнего течения реки Раздан. Исследования проводились в 2019–2020 гг., были обследованы 454 особи 15 видов рыб. Обнаруженная гельминтофауна характеризовалась невысоким видовым разнообразием, в результате выявлено 5 видов гельминтов: 1 вид Monogenea, 1 вид Trematoda, 2 вида Cestoda и 1 вид Nematoda. Общая инвазированность рыб гельминтами составила 34.1%. Обнаруженные гельминты были локализованы в основном в полости тела, кишечнике, хрусталиках глаз и на жабрах рыб. Наибольшее количество видов гельминтов отмечалось у храмуль и карасей. Практически на всех исследуемых участках нижнего течения реки наиболее распространенными из обнаруженных видов гельминтов были плероцеркоиды цестоды Ligula intestinalis (L., 1758) и метацеркарии трематод Diplostomum sp. Nordmann, 1832. Data from studies of the species composition of the fish helminth fauna and the degree of fish infection in the lower reaches of the Hrazdan River are presented. The studies were conducted in 2019–2020; 454 individuals of 15 fish species were examined. The detected helminth fauna was characterized by low species diversity, as a result, 5 species of helminths were identified: 1 species of Monogenea, 1 species of Trematoda, 2 species of Cestoda and 1 species of Nematoda. The total infection of fish by helminths was 34.1%. The detected helminths were localized mainly in the body cavity, intestine, eye lenses and on the gills of fish. The largest number of helminth species was noted in khramicarps and crucian carps. In almost all the studied areas of the lower reaches of the river, the most common of the detected species of helminths were plerocercoids of the cestode Ligula intestinalis (L., 1758) and metacercariae of the trematode Diplostomum sp. Nordmann, 1832.

Приведены данные исследований видового состава гельминтофауны и степени инвазированности рыб нижнего течения реки Раздан. Исследования проводились в 2019–2020 гг., были обследованы 454 особи 15 видов рыб. Обнаруженная гельминтофауна характеризовалась невысоким видовым разнообразием, в результате выявлено 5 видов гельминтов: 1 вид Monogenea, 1 вид Trematoda, 2 вида Cestoda и 1 вид Nematoda. Общая инвазированность рыб гельминтами составила 34.1%. Обнаруженные гельминты были локализованы в основном в полости тела, кишечнике, хрусталиках глаз и на жабрах рыб. Наибольшее количество видов гельминтов отмечалось у храмуль и карасей. Практически на всех исследуемых участках нижнего течения реки наиболее распространенными из обнаруженных видов гельминтов были плероцеркоиды цестоды Ligula intestinalis (L., 1758) и метацеркарии трематод Diplostomum sp. Nordmann, 1832. Data from studies of the species composition of the fish helminth fauna and the degree of fish infection in the lower reaches of the Hrazdan River are presented. The studies were conducted in 2019–2020; 454 individuals of 15 fish species were examined. The detected helminth fauna was characterized by low species diversity, as a result, 5 species of helminths were identified: 1 species of Monogenea, 1 species of Trematoda, 2 species of Cestoda and 1 species of Nematoda. The total infection of fish by helminths was 34.1%. The detected helminths were localized mainly in the body cavity, intestine, eye lenses and on the gills of fish. The largest number of helminth species was noted in khramicarps and crucian carps. In almost all the studied areas of the lower reaches of the river, the most common of the detected species of helminths were plerocercoids of the cestode Ligula intestinalis (L., 1758) and metacercariae of the trematode Diplostomum sp. Nordmann, 1832.

Приведены результаты исследования видового состава ихтиофауны р. Ахурян до и после малой гидроэлектростанции (МГЭС) «Амасия», проведенного в 2018–2019 гг. Отмечено 12 видов рыб. Впервые изучение видового состава рыб р. Ахурян было проведено с помощью электролова. Наибольшее число видов (7) было зафиксировано весной 2019 г. в нижнем течении реки у пос. Мармашен, наименьшее (3 вида) – осенью 2018 года на участках отбора проб вблизи МГЭС «Амасия» после водозабора и на притоке реки Ахурян. На всех станциях вылова рыб были отмечены восточная быстрянка Alburnoides eichwaldii De Filippi, 1863 и куринский усач Barbus cyri De Filippi, 1985. В осенний период восточная быстрянка была супердоминантом на всех исследованных участках. Весной 2019 г. в нижнем течении реки быстрянка стала доминируюшим видом. Отсутствие куринской храмули Capoeta capoeta Guldenstadt, 1772 в местах отбора проб вблизи МГЭС после точки водозабора и вблизи плотины на реке между поселками Капс и Джрадзор, вероятно, является результатом влияния МГЭС. За период исследований на обследуемой территории из рыб, занесенных в Красную книгу Армении как находящихся под угрозой исчезновения, был обнаружен только жерех Leuciscus aspius Linnaeus, 1758. Fish species composition in the Akhuryan River upper and below a small hydroelectric power plant (SHPP) “Amasia” was investigated (2018-2019). Twelth fish species have been identified. For the first time, electrofishing was used for determining fish composition. The highest fish diversity (seven species) was recorded in the spring 2019 in the lower reach of the river near the village of Marmashen, while the lowest (three species) in the autumn 2018 near the SHPP “Amasia” below the water intake point and in the tributary of the Akhuryan. At all fish sampling sites, Kura chub – Alburnoides eichwaldii De Filippi 1863 and Kura barbell – Barbus cyri De Filippi 1985 were met. In autumn, Kura chub were a super-dominating species in all the sites. In the spring 2019, they were dominating in the lower reach of the river. The absence of Kura khramicarp Capoeta capoeta Guldenstadt 1772 below the SHPP’s water intake point and near the dam on the river between the villages Caps and Jradzor was likely the result of SHPP operation. The only listed fish species (status “endangered” in The Red Book of Armenia) found during the study period was the asp Leuciscus aspius Linnaeus 1758.

Lake Sevan is a freshwater reservoir in the Caucasus region. Since the first half of the 20th century, the lake has undergone significant changes caused by human activity and anthropogenic pressure. To identify the current ecological state of two bays—Lchashen and Lichk—located in different parts of the lake, a study was conducted in 2022–2023 using a multi-biomarker approach. For this purpose, biomarkers for assessing the health status of fish and the quality of their living conditions were used such as the activity of acetylcholinesterase (AChE) in the brain, glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and the concentration of reduced glutathione (RGS) and malondialdehyde (MDA) in the liver and gills of the whitefish (Coregonus lavaretus Linnaeus, 1758). In addition, hydrochemical and ichthyological analyses were conducted. This study demonstrated seasonal dynamics for all biomarkers. Comparative analysis of biomarkers and hydrochemical and ichthyological data showed that the whitefish in Lchashen Bay is in worse health, and its living conditions there are less favorable than in Lichk Bay.

Long-term features of the vertical and horizontal structure of water temperature field in Lake Sevan are discussed. It is shown that the climate warming has led to an increase in epilimnion temperature in Bol’shoi Sevan in July by 2.0‒3.0°C. The increase in water temperature in hypolimnion was not greater than 1.1°C. In autumn (October), the epilimnion became 1.2°C warmer, while hypolimnion temperature practically has not changed on the average over years. Temperature fields were used to calculate the density currents in summer and autumn periods. A dominating cyclonic water circulation was revealed all over the lake, confirmed by chlorophyll distribution by satellite image data. In the case of large horizontal gradients of water density, the flow velocity can reach 50 cm/s. Autonomous buoy stations revealed a wide range of water temperature variations due to internal waves of different nature. The reversible vertical mixing of water mass by internal waves plays an important role in the distribution of nutrients and plankton within the water mass. The water level rise by ~3 m, unlike it drop by 1981 by 18.48, has not caused any significant changes in lake hydrological regime.