Freshwater Reservoir Research Articles

A brief review on effect of heavy metals in fish fauna

The variety of fish species is essential for the well-being and stability of aquatic environments. Fishes are one of the most important aquatic creatures that are directly or indirectly related to human health and wealth. With thousands of different species inhabiting various water bodies around the world, each fish contributes to the overall biodiversity and sustainability of these environments. Humans have long relied on aquatic resources for food, medicines, and materials. Fish species are adapted to a variety of environments such as freshwater lakes, rivers, reservoirs, oceans, and estuaries. The diversity of habitats available allows a variety of fish species to thrive in different environments. Fish diversity is a vital component of aquatic ecosystems, supporting ecosystem stability, economic value, and cultural significance. India's inland water resources are abundant and diverse, including reservoirs that play an important role in the country's inland fisheries sector.Biodiversity and its conservation are considered one of the key issues to enable sustainable use of natural resources. Protecting ichthyophan diversity in its natural habitat is essential and the need of the hour. By understanding the factors that influence fish diversity and the importance of preserving biodiversity, we can work towards protecting and protecting these priceless resources for upcoming generations.

Assessing microplastic abundances in freshwater fishes in a subtropical African reservoir

Microplastics are emerging pollutants of global concern, and their presence in the aquatic environment poses a serious risk for aquatic biota. While many studies have been conducted on the presence of microplastics in marine habitats, little research has been done in freshwater African reservoirs on microplastic pollution and their impacts on fish within the subtropical regions. To bridge this gap, the current study investigated microplastic abundances and distribution in freshwater fish within Nandoni reservoir, South Africa, across two seasons (i.e., hot–wet, cool–dry). Fish were randomly sampled using seine and gill nets from seven sites within the reservoir. In the laboratory, fish were then sorted according to taxa before dissecting them to remove the gills and the gastrointestinal tract (GIT). The organs were digested using hot hydrochloric acid and hydrogen peroxide, and the microplastics were classified according to their colours and shapes. Among the 94 fishes (i.e., 8 species) examined, microplastics were detected in 86.6% of the eight species caught. Microplastics were dominant in the gills and GIT during the cool–dry and hot–wet seasons, respectively. High microplastic abundances were found in the gills of Micropterus salmoides and the GIT of Coptodon rendalli, where fibres and the transparent colour were the most dominant. The results further showed high microplastic abundances in benthopelagic feeders highlighting that habitat influences fish consumption of microplastics whether directly or indirectly. Significant differences were observed in the feeding zone and season for all microplastic types. Microplastic sources in the reservoirs could be due to anthropogenic activities such as illegal dumping, fishing, and agriculture. Thus, there is a need for further investigation into the relation of fish weight, fish sex and body in relation to microplastic pollution. The highlighted ecological factors should be taken into consideration for future research and management actions aimed at mitigating and protecting the negative impacts of microplastic pollution on environmental and human health.

Multi-proxy investigations of Bronze Age diet and environment in the hyper-arid eastern Tarim Basin (Lop Nur), northwest China

Humans have a long history of occupying ecologically marginal regions, and the ancient cultural mechanisms of adaptation to these challenging environments remain poorly understood. We examine archaeological deposits from a Bronze Age settlement in the hyper-arid eastern Tarim Basin (Lop Nur), identifying well-preserved plant remains and bone fragments that shed light on the palaeodiet and past environmental setting. We use the newly developed peptide mass fingerprinting method of ZooMS (zooarchaeology by mass spectrometry) and TimsTOF MS (trapped ion mobility time of flight mass spectrometry) to identify fragments of ancient fish bones as Cyprinidae and possible Salmonidae, indicating both their consumption and the former presence of intra-settlement fresh water-bodies. Remains of littoral and aquatic plants attest to a marshy palaeo-delta at the confluence of the Tarim and Kongque rivers, testifying to a former biodiverse oasis in the Lop Desert when humans occupied the site. We conclude that the use of both aquatic and desert peripheral resources, combined with the intentional management of local environments, were all essential prehistoric adaptations. In addition, we show that radiocarbon dates of aquatic remains have an offset spanning hundreds to thousands of years, due to a freshwater reservoir effect, requiring careful consideration of ages for archaeological bones in the broader region.

Assessment of the Health Status of Whitefish (Coregonus lavaretus Linnaeus, 1758) and the Quality of Its Habitat in Lake Sevan (Armenia) Using a Multi-Biomarker Approach

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.

Causes and consequences of natural and anthropogenically induced late Holocene hydrological variations on the largest freshwater system in the Lesser Caucasus (Lake Sevan, Armenia)

Although Lake Sevan is the largest freshwater reservoir in the Caucasus, no paleohydrological or paleoenvironmental investigations have been carried out on profundal sediments so far. Here we present high-resolution sedimentological results from a 141 cm-long sediment core covering the past 4870+190/-245 cal a BP. The chronology is based on a combination of 137Cs/210Pb and radiocarbon dating supported by paleomagnetic secular variation stratigraphy, providing new inclination and declination data for the Caucasus. The time frame covered by this sequence is characterized by a long-term lake level rising trend superimposed by smaller-scale hydrological variations which is in agreement with the rest of the Lake Sevan basin. In the presented sedimentary sequence, the superimposed hydrological variations seem to be coherent with the Hallstatt and Eddy cycles.A distinct shift towards wetter conditions is observed between 2500 and 2000 cal a BP resulting in a very high lake level. An artificial lake level drop of about 20 m in the 20th century led to anoxic conditions similar to the ones during a low lake level at 4870+190/-245 cal a BP. This study shows that under natural conditions Lake Sevan was able to recover from this oxygen deficit when the lake level increased, implying that this would also happen to the artificially lowered lake today if the lake level were raised.

Direct observations of evapotranspiration from three contrasting vegetation types on a coastal low-lying sub-tropical sand island

Coastal low-lying sand islands confront an imminent threat owing to global warming, primarily stemming from the confluence of rising sea levels and amplified precipitation variability. These islands harbour delicate freshwater reservoirs in unconfined aquifers, reliant significantly upon precipitation for replenishment. This investigation focuses on a sand island situated along Australia’s eastern coast, resembling islands prevalent across the Indian and Pacific Oceans. The study involves comprehensive instrumentation to monitor Actual Evapotranspiration (AET) concurrently with rainfall patterns and water table fluctuations. Eddy Covariance (EC) systems were employed across three distinct vegetation zones: a wetland, a swamp, and a commercially managed pine forest plantation. The aim was to gauge evapotranspiration dynamics, comparing computed reference evapotranspiration (ET0) at each site with EC-measured values to establish novel reference vegetation coefficients (Kv) tailored to these specific environments. Actual evapotranspiration was found the largest at the wetland, the swamp, and the pine plantation in decreasing order. Pine plantation evapotranspiration was found the most sensitive to water table depth, while the native swamp and wetland maintained high evapotranspiration rates through dry periods. A simple idealized water balance is proposed for the island for the dry and wet seasons. Large rainfall events during the wet season were found critical in providing recharge of the aquifer, highlighting the importance of such events in maintaining the freshwater resource and vegetation health on such islands.

Analysis of the environmental state of the Sarata River in Odesa Region

The relevance of the study is dictated by the need to preserve the water resources of southern Ukraine and ensure their good environmental condition. In the context of military operations, Odesa Region plays a key role in providing the country with agricultural products because of significant damage incurred to agricultural lands of Mykolaiv and Kherson Regions in the course of military actions. Hence the role of irrigation and the need to restore and modernize irrigation systems are growing. One of fresh water reservoirs of Odesa Region is Sasyk reservoir (artificially created as part of the estuary) which accumulates fresh water supplied from the Danube. The Kogylnyk and the Sarata rivers flow into the northern part of the reservoir and can worsen its hydroecological condition. The subject of the study: pollution of the rivers across North-Western Black Sea Coast by chemicals. The object of the study: the environmental state of the Sarata River. The study is aimed at assessing the environmental state and environmental risks of chemical pollution of the Sarata River. The water quality assessment was performed based on a modified version of water pollution index (WPI). Biogenic substances (ammonium nitrogen, nitrite nitrogen, nitrate nitrogen) were identified as the main pollutants. The content of chlorides and sulfates is also significant. The assessment of the pollution risks by biogenic substances is based on calculations of the statistical probit function. The source materials of the research include hydrochemical observations made by the State Agency of Water Resources of Ukraine for the period from 2007 to 2023 in the upper reaches of the Sarata River - village of Miniailivka (94 km from the mouth, near the border with Moldova) and in the lower reaches of the Sarata River - village of Bilolissya (14.3 km from the mouth). The analysis of probability of exceeding the MPC for fishery use indicated that, in terms of nitrite ions and nitrate ions, such probability is higher in the upper basin than in the lower one. According to other indicators, the probability of exceeding the MPC by pollutants is either almost the same or slightly increased in the lower reaches. The assessment of water quality according to the modified WPI (dissolved oxygen, BOD5, ammonium, nitrite and nitrate ions, phosphates) showed that the water quality in the Sarata River mainly belongs to the "moderately polluted" and "polluted" classes. According to the environmental risk indicators, it was established that the possibility of a "high" risk of contamination by biogenic substances does prevail. Its probability is 52.9% for the upper reaches and 60% for the lower reaches. The "high" level of class IV pollution (ER=0.60-0.79) corresponds to an "unsatisfactory" environmental condition. The probability of achieving the class of a "good" environmental condition (class II, ER=0.20-0.39) is quite small: 17.6% in the upper reaches and only 6.67% in the lower reaches. Thus, the Sarata River belongs to such rivers, the natural properties of which underwent significant changes as a result of sewage delivery from "Sarata Komunservis" utility enterprise, settlement of Sarata. Contaminated waters are unsuitable for drinking, household and sports purposes, as well as for fish farming. The quality of the Sarata River's water has a negative impact on the environmental state of Sasyk reservoir.

Pannonibacter tanglangensis sp. nov., a New Species Isolated from Pond Sediment.

Two bacterial strains (XCT-34T and XCT-53) isolated from sediment samples of an artificial freshwater reservoir were analyzed using a polyphasic approach. The two isolates are aerobic, Gram-stain-negative, oxidase-negative, catalase-positive, motile with polar flagella, rod-shaped, and approximately 1.4-3.4 × 0.4-0.9μm in size. Phylogenetic analyses based on 16S rRNA gene and whole-genome sequences showed that the two strains formed a distinct branch within the evolutionary radiation of the genus Pannonibacter, closest to Pannonibacter carbonis Q4.6T (KCTC 52466). Furthermore, lower than threshold average nucleotide identity values (ANI, 85.7-86.4%) and digital DNA-DNA hybridization values (dDDH, 22.3-30.5%) of the two strains compared to the nearest type strains also confirmed that they represented a novel species. Genomic analyses, including annotation of the KEGG pathways, prediction of the secondary metabolism biosynthetic gene clusters and PHI phenotypes, supported functional inference and differentiation of the strains from the closely related taxa. Results of chemotaxonomic and physiological studies revealed that their distinct phenotypic characteristics distinguished them from existing Pannonibacter species. Thus, the two strains are considered to represent a novel species of Pannonibacter, for which the name of Pannonibacter tanglangensis sp. nov. is proposed, with XCT-34T (= KCTC 82332T = GDMCC 1.1947T) as the respective type strain.

Photo responsive single layer MoS2 nanochannel membranes for photocatalytic degradation of contaminants in water

The major polluting aspects of our global fashion industries are the textile wastewater that turns black all our freshwater reservoirs. Nano-filtration through membrane technology is one of the biggest solutions of industrial wastewater treatment but the fouling of membrane is the major limitation of previous work. In this research, novel PVDF/MoS2-TNT (PMT) nanocomposite membranes were fabricated through a modified In-situ polymerisation phase inversion method. X-ray diffraction (XRD) analysis also confirmed the β-phase of PVDF within the developed PVDF/MoS2-TNT membrane. XPS analysis provides evidence about the presence of a specific chemical states of titanium nanotube and molybdenum disulphide which is involved in the photocatalytic degradation of pollutant molecules. Scanning electron microscope (SEM) shows that our membranes are porous in nature. PVDF/MoS2-TNT membranes exhibit excellent filtration efficiency (∼97%) for textile wastewater. The results and outcomes of the research demonstrate that PMT membranes have enormous potential in the commercial application of textile wastewater treatment.

Exploratory Analysis Using Deep Learning for Water-Body Segmentation of Peru's High-Mountain Remote Sensing Images.

High-mountain water bodies represent critical components of their ecosystems, serving as vital freshwater reservoirs, environmental regulators, and sentinels of climate change. To understand the environmental dynamics of these regions, comprehensive analyses of lakes across spatial and temporal scales are necessary. While remote sensing offers a powerful tool for lake monitoring, applications in high-mountain terrain present unique challenges. The Ancash and Cuzco regions of the Peruvian Andes exemplify these challenges. These regions harbor numerous high-mountain lakes, which are crucial for fresh water supply and environmental regulation. This paper presents an exploratory examination of remote sensing techniques for lake monitoring in the Ancash and Cuzco regions of the Peruvian Andes. The study compares three deep learning models for lake segmentation: the well-established DeepWaterMapV2 and WatNet models and the adapted WaterSegDiff model, which is based on a combination of diffusion and transformation mechanisms specifically conditioned for lake segmentation. In addition, the Normalized Difference Water Index (NDWI) with Otsu thresholding is used for comparison purposes. To capture lakes across these regions, a new dataset was created with Landsat-8 multispectral imagery (bands 2-7) from 2013 to 2023. Quantitative and qualitative analyses were performed using metrics such as Mean Intersection over Union (MIoU), Pixel Accuracy (PA), and F1 Score. The results achieved indicate equivalent performance of DeepWaterMapV2 and WatNet encoder-decoder architectures, achieving adequate lake segmentation despite the challenging geographical and atmospheric conditions inherent in high-mountain environments. In the qualitative analysis, the behavior of the WaterSegDiff model was considered promising for the proposed application. Considering that WatNet is less computationally complex, with 3.4 million parameters, this architecture becomes the most pertinent to implement. Additionally, a detailed temporal analysis of Lake Singrenacocha in the Vilcanota Mountains was conducted, pointing out the more significant behavior of the WatNet model.

Carbon dioxide emissions from temperate reservoirs and pit lakes of different trophic states

The abundance of human-made inland waters, such as artificial ponds and reservoirs, has multiplied over the last decades. Compared to natural lakes, reservoirs and retention basins can exhibit a higher accumulation of organic carbon and a higher emission of greenhouse gases. Magnitude and dynamics of related emission fluxes are important to understand the role of inland waters in the global carbon cycle. However, origin and use of artificial waterbodies are diverse, and it is unclear whether current gas flux estimates adequately represent all important types and conditions of artificial inland waters. This study compares drivers of CO2 and CH4 emissions from two types of temperate artificial waters that are widespread in central Europe: reservoirs and artificial lakes in former open-pit lignite mines (pit lakes). We measured CO2 exchange at the water surface, calculated surface water CO2 from long-term DIC and pH data, and measured CO2 and CH4 concentrations throughout the water column. We found that an older, eutrophic pit lake showed seasonal variations in CO2 fluxes including uptake during summer and release during turnover, similar to three studied freshwater reservoirs. In contrast, reacidification and repeated addition of carbonate (liming) led to sustained CO2 supersaturation in a young, oligotrophic pit lake throughout the year, potentially making it a steady source of CO2 to the atmosphere. This implies that on an annual level, pH regulation and lake maturity largely determine whether pit lakes act as sources of CO2 (young, slightly acidic) or sinks of CO2 (older, neutral pH).

Ecological Potential of Freshwater Dam Reservoirs Based on Fish Index, First Evaluation in Poland

A pilot ichthyological index was developed for use within the Water Framework Directive in the area of Central and Eastern Europe for dam reservoirs, which are heavily modified water bodies. This is the first approach to assessing this water body type based on ichthyofauna in Poland. Various fishing gear types were used. The tested dam reservoirs were scattered throughout the country, from lowland to mountainous areas, with very diverse hydrological and morphological characteristics and pressure ranges based on the TSI index. In preliminary work, a correlation matrix with the TSI index’s pressure indicator was tested based on the abundance or biomass of fish species, fish families present, fishing gear used, and fishing depth range for a total of 588 cases. As a result of the tests carried out, the preliminary indicator was based on the ratio of the number of the two families Cyprinidae and Percidae. The correlation between the developed indicator and the pressure index was strong (r = 0.77; p < 0.001). The Percidae family exhibited a strong correlation with the most connections in the matrix. Based on the obtained results, the principle of using already confirmed relationships, such as the ratio between Cyprinidae and Percidae fish families, in the assessment of eutrophication was confirmed to be effective, guaranteeing the effective initial assessment of ecological potential.

Development of a multidecadal land reanalysis over High Mountain Asia

Anthropogenic and climatic changes affect the water and energy cycles in High Mountain Asia (HMA), home to over two billion people and the largest reservoirs of freshwater outside the polar zone. Despite their significant importance for water management, consistent and reliable estimates of water storage and fluxes over the region are lacking because of the high uncertainties associated with the estimates of atmospheric conditions and human management. Here, we relied on multivariate data assimilation (MVDA) to provide estimates of energy and water storage and fluxes that reflect the processes occurring in the region such as greening and irrigation-driven groundwater depletion. We developed and employed an ensemble precipitation estimate by blending different precipitation products thereby reducing the uncertainties and inconsistencies associated with precipitation in HMA. Then, we assimilated five variables that capture the changes in hydrology in response to climate change and anthropogenic activities. Overall, our results have shown that MVDA has allowed a better representation of the land surface processes including greening and irrigation-driven groundwater depletion in HMA.

Ecological Assessment and Molecular Characterization of Spirulina in Freshwater Reservoirs of Kohat, Pakistan

Ecological Assessment and Molecular Characterization of Spirulina in Freshwater Reservoirs of Kohat, Pakistan

Abiotic Factors and The Growth of Cyanobacteria in Surface Water Reservoirs in The State of Pernambuco

Objective: Analyze the relationship between physical-chemical and climatic abiotic factors in relation to the occurrence of cyanobacteria genera in surface water reservoirs used for public supply in the state of Pernambuco. Literature Review: Information is presented on cyanobacteria and the consequences of the release of untreated effluents on the eutrophication of surface waters with effects on the growth of cyanobacteria and consequences for aquatic organisms and humans and the climate in regions of Pernambuco where water reservoirs are located. Method: Quali-quantitative descriptive and exploratory approach to the analysis of abiotic variables (pH, C.E., Turbidity, Color, Calcium, Magnesium, Chlorides, Sulfate, Nitrogen, Phosphate, Alkalinity, Hardness, Iron, Manganese, Aluminum and rainfall) and biotic (Cyanobacteria density), collected from the Pernambuco Sanitation Company – COMPESA. The samples were from eutrophic freshwater reservoirs in Pernambuco collected between 2010 and 2020. Results and Discussion: The most frequent genus of cyanobacteria was Raphidiopsis/Cylindrospermopsis, found abundantly in all reservoirs, where the increase in color, turbidity and pH were positively correlated with the presence of Microcystis and Raphidiopsis/Cylindrospermopsis, and negatively with the increase in toughness. A positive correlation was also observed between hardness and the increase in Planktothrix density. Research Implications: Generate guidelines for drinking water supply services, presenting tools for understanding abiotic conditions that influence the growth of cyanobacteria, in order to outline control or mitigation strategies in ETAs. Originality/Value: Generate useful information in the evaluation of abiotic parameters and cyanobacteria density, observed over a long period (10 years), showing positive/negative correlations in surface waters used for human consumption.

Techno-Economic Analysis of Atmospheric Water Harvesting Across Climates.

Drinking water scarcity is a global challenge as groundwater and surface water availability diminishes. The atmosphere is an alternative freshwater reservoir that has universal availability and could be harvested as drinking water. In order to effectively perform atmospheric water harvesting (AWH), we need to (1) understand how different climate regions (e.g., arid, temperate, and tropical) drive the amount of water that can be harvested and (2) determine the cost to purchase, operate, and power AWH. This research pairs thermodynamics with techno-economic analysis to calculate the water productivity and cost breakdown of a representative condensation-based AWH unit with water treatment. We calculate the monthly and annual levelized cost of water from AWH as a function of climate and power source (grid electricity vs renewable energy from solar photovoltaics (PV)). In our modeled unit, AWH can provide 1744-2710 L/month in a tropical climate, 394-1983 L/month in a temperate climate, and 37-1470 L/month in an arid climate. The levelized cost of water of AWH powered by the electrical grid is $0.06/L in a tropical climate, $0.09/L in a temperate climate, and $0.17/L in an arid climate. If off-grid solar PV was purchased at the time of purchasing the AWH unit to power the AWH, the costs increase to $0.40/L in an arid climate, $0.17/L in a temperate climate, and $0.10/L in a tropical climate. However, if using existing solar PV there are potential cost reductions of 4.25-5-fold between purchasing and using existing solar PV, and 2-3-fold between using the electrical grid and existing solar PV, with the highest cost reductions occurring in the tropical climate. Using existing solar PV, the levelized cost of AWH is $0.09/L in an arid climate, $0.04/L in a temperate climate, and $0.02/L in a tropical climate.

Phytoplankton community structure in the dry zone reservoirs of Sri Lanka at the declining phase of the tropical monsoon

We studied the phytoplankton community structure and their relationship to the physicochemical properties of water by selecting five major freshwater reservoirs; Bandagiriya, Kattakaduwa, Lunugamvehera, Ridiyagama, and Tissa in the Southern dry zone of Sri Lanka during the declining phase of tropical monsoon rainfall (December 2019 to January 2020). Fifty-seven species, dominated by Cyanophyta (63%), followed by Chlorophyta, Bacillariophyta, and Euglenophyta were identified morphologically and through DNA sequencing. The majority of Cyanophyta were filamentous forms (62%) with approximately 88% being cyanotoxin producing species. The species composition of phytoplankton communities is reservoir specific. Microcystis was dominant in Lunugamvehera while the diatom Melosira was dominant in Ridiyagama, Kattakaduwa and Tissa. The lowest phytoplankton density and diversity were observed in Bandagiriya mainly due to high turbidity and total suspended solids which interfere with light penetration through the water column. Physicochemical properties of water were significantly different among reservoirs, leading to reservoir specific correlations between phytoplankton density and physicochemical properties of water which might have been driven by the inter-correlative effects of biotic and abiotic factors at the time of sampling. Therefore, the interactive effects might be responsible for the observed variations in phytoplankton community composition. Thus, the present study provides important information on the phytoplankton community structure at the onset of successional episodes in five tropical freshwater reservoirs in relation to their spatial variations in hydrological regimes and physicochemical properties. Such data would provide essential information for planning and implementation of reliable and efficient strategies for monitoring, sampling, forecasting, and managing algal blooms.

Development of an Ecosystem Model Considering Sediment Redox Processes in Enclosed Water Bodies

This study investigates enclosed water bodies to understand the intricate interactions among physical, chemical, and biological processes. A one-dimensional model, integrating sediment and ecosystem components, was developed to analyze oxygen depletion, nutrient dynamics, and the influence of sediment organic matter on oxygen concentrations due to stratification. Oxygen and nutrient concentrations were derived by combining results from a one-dimensional vertical diffusion model with the ecosystem model. The dissolution, adsorption, and desorption of inorganic substances in bottom mud react differently under anaerobic and aerobic conditions, necessitating separate formulations for reduction and oxidation reactions in the bottom mud model. In Lake Biwa, Japan’s largest lake, dissolved oxygen levels have decreased despite regulatory efforts since the 1970s, prompting an investigation into the causes of oxygen-depleted water masses. The model was thus applied to examine oxygen consumption in Lake Biwa’s deep sediments, shedding light on anoxia in enclosed water bodies. This study emphasizes the significance of bottom sediments in water quality models and their implications for ecosystems. Furthermore, the adaptive nature of this model allows for its application in various water bodies, including freshwater reservoirs, lakes, and saltwater bays.

Gender-specific responses in gene expression of Nile tilapia (Oreochromis niloticus) to heavy metal pollution in different aquatic habitats

Monitoring heavy metal accumulation is essential for assessing the viability of aquatic ecosystems. Our methodology involved integrating analysis of immunological, stress, inflammatory, and growth-related gene expression in male and female Nile tilapia with on-site recordings of physicochemical parameters. Additionally, we assessed the effect of different physicochemical parameters on heavy metal bioavailability and residual concentration in fish and water. Samples of fish and water were gathered from three different localities: Lake Brullus, a brackish lake sited in northern Egypt; Lake Nasser, an artificial freshwater reservoir located in southern Egypt; and El-Qanater El-Khayria, a middle-freshwater location belonging to the Rashid branch of the river Nile. The assessment of heavy metal residues (Fe, Cu, Zn, Mn, and Ni) revealed that their concentrations were higher in fish specimens compared to their counterparts in water (except for Ni). In addition, Lake Brullus emerges as the most polluted area, exhibiting elevated levels of heavy metals concentrations in water and fish specimens. In contrast, Lake Nasser showed the least degree of heavy metals pollution. Gene expression analysis revealed gender-specific responses to heavy metal exposure at the three investigated water bodies. The expression of hepatic antioxidant genes (GST and MT) and inflammatory-related genes (CC-chemokine and TNFα) increased in males compared to females. In females, the immune and pro-inflammatory-related genes (IgM and CXC2-chemokine) transcripts were upregulated. Additionally, growth-related genes were downregulated in both Lake Brullus and El-Qanater; on the contrary, fish samples from Lake Nasser exhibited a normal expression pattern of growth-related genes. Stress-related genes (HSP70 and HSP27) showed significant downregulation in gills of both genders from Lake Brullus. The minimal presence of heavy metal contaminants in Lake Nasser seems to endorse the normal patterns of gene expression across all gene categories. A potential gender-specific gene expression response towards pollution was noticed in genes associated with inflammation and antioxidant activities. This highlights the importance of considering gender-related responses in future environmental assessments.

The diversity and risk of potential pathogenic bacteria on the surface of glaciers in the southeastern Tibetan Plateau

Glaciers, which constitute the world's largest global freshwater reservoir, are also natural microbial repositories. The frequent pandemic in recent years underscored the potential biosafety risks associated with the release of microorganisms from the accelerated melting of glaciers due to global warming. However, the characteristics of pathogenic microorganisms in glaciers are not well understood. The glacier surface is the primary area where glacier melting occurs that is often the main subject of research on the dynamics of pathogenic microbial communities in efforts to assess glacier biosafety risks and devise preventive measures. In this study, high-throughput sequencing and quantitative polymerase chain reaction methods were employed in analyses of the composition and quantities of potential pathogenic bacteria on the surfaces of glaciers in the southeastern Tibetan Plateau. The study identified 441 potential pathogenic species ranging from 215 to 4.39 × 1011 copies/g, with notable seasonal and environmental variations being found in the composition and quantity of potential pathogens. The highest level of diversity was observed in April and snow, while the highest quantities were observed in October and cryoconite. Host analysis revealed that >70 % of the species were pathogens affecting animals, with the highest proportion of zoonotic pathogens being observed in April. Analysis of aerosols and glacial meltwater dispersion suggested that these microbes originated from West Asia, primarily affecting the central and southern regions of China. Null model analysis indicated that the assembly of potential pathogenic microbial communities on glacier surfaces was largely governed by deterministic processes. In conclusion, potential pathogenic bacteria on glacier surfaces mainly originated from the snow and exhibited significant temporal and spatial variation patterns. These findings can be used to enhance researchers' ability to predict potential biosafety risks associated with pathogenic bacteria in glaciers and to prevent their negative impact on populations and ecological systems.