重金属汞对水域的影响

The contamination of micro-plastics (MPs)/nano-plastics (NPs) in environment poses a global concern, necessitating a scientific evaluation of their potential risks to ecosystems and organisms. We herein investigated the adsorption kinetics of different mercury species including inorganic mercury (Hg2+), methylmercury (MeHg) and ethylmercury (EtHg) on three different MPs, such as polyethylene MPs (PE MPs), polypropylene MPs (PP MPs) and polystyrene MPs (PS MPs) in micro-polluted water in detail, and further evaluated the individual and combined cytotoxicity of polystyrene NPs (PS NPs)/polypropylene NPs (PP NPs) and different mercury species. The results indicated that EtHg undergoes demethylation partly to form Hg2+ during the adsorption process on PP MPs, and the adsorption kinetics of Hg2+, MeHg and EtHg on three MPs fitted with pseudo-first-order (PFO) model in initial stage and simultaneously fitted with pseudo-second-order (PSO) model during whole adsorption process. This suggested that adsorption of mercury species on three MPs we driven mainly by physical process in initial stage and by chemical process during whole absorption process. In natural micro-polluted water, the equilibrium adsorption capacities (Qe) of Hg2+ on three MPs (156.3-270.3 ng/g) are much higher than that of MeHg (5.562-78.13 ng/g) and EtHg (7.831-70.42 ng/g). Cytotoxicity experiments revealed that PP NPs and PS NPs themselves have little cytotoxicity, but the presence of them can enhance the cytotoxicity of mercury species, showing NPs size-depended and mercury species-depended synergistic toxic effect. The findings of this study provided valuable insights for scientifically evaluating the potential risk of MPs/NPs to ecosystems and organisms.

Nanoplastics (NPs) and mercury (Hg) are ubiquitous pollutants that co-occur in aquatic ecosystems. However, the interaction between NPs and Hg, particularly whether NPs affect the accumulation and in vivo biotransformation of Hg in aquatic organisms, remains unclear. The toxicity of NPs and mercuric chloride (HgCl2), both individually and in combination at environmentally relevant concentrations, on rare minnow (Gobiocypris rarus) were investigated in this study. The results demonstrated that NPs increased total Hg accumulation by 33.33 % but had limited effects on methylmercury (MeHg) content and its proportional distribution in muscle tissue compared to single Hg exposure. Both NPs and Hg induced significant growth inhibition, intestinal damage, oxidative stress, and inflammatory responses in rare minnow, with endpoint-specific effect patterns. Moreover, NPs and Hg dramatically altered gut microbiota composition and co-occurrence networks, with NPs inducing more metabolic pathway changes than Hg. Notably, combined exposure exacerbated almost all toxic effects in rare minnow compared to individual exposures, indicating synergistic interactions between NPs and Hg. These findings highlight the need to consider co-existing contaminants when evaluating NP toxicity.

Human activities have caused significant ecological disruptions in aquatic environments, affecting fish behavior and threatening ecosystem stability. Mercury pollution, stemming from industrial and mining activities, infiltrates water bodies and accumulates in fish tissues, disrupting their neurological functions. This leads to altered behaviors such as disoriented swimming, impaired predator avoidance, and compromised foraging, jeopardizing their survival and ecological interactions. The bio magnification of mercury intensifies its toxic effects up the food chain, particularly affecting predatory fish. Microplastics, ubiquitous in water bodies due to human consumption and waste, pose another significant threat. Fish ingest these particles, which accumulate in their digestive systems and induce stress responses that alter behavior, reduce feeding activity, and impair reproduction. Thermal water discharge, a consequence of industrial processes and power generation, causes thermal stress in fish. This alters their behavior, forces changes in habitat and migration patterns, and exacerbates oxygen depletion, further compromising fish health. Pesticides entering waterways via runoff disrupt fish neurotransmitter systems and affect sensory perception, motor coordination, and reproductive behavior. Pharmaceutical pollutants like fluoxetine, an antidepressant, disrupt fish neurotransmitter systems, affecting behaviors such as swimming patterns, reduced foraging, and impaired predator avoidance. These pollutants can cascade through aquatic food webs, influencing community dynamics. Fish suffocate due to algal blooms that reduce oxygen levels, changing their behavior and habitat suitability. Eutrophication is caused by wastewater discharge and agricultural runoff. Addressing these multifaceted threats through sustainable practices is critical to preserving aquatic ecosystems and ensuring the long-term health of fish populations worldwide.

The use of mercury in industry causes its continuous increase in nature. A pro-ecological technology that can reduce mercury levels in aquatic environments is phytoremediation using the plant Salvinia natans. The study aimed to determine the maximum mercury concentration for effective phytoremediation using Salvinia natans. The study aimed to determine the threshold for effective phytoremediation using Salvinia natans. A Microtox screening test was performed for concentrations ranging from 0.15 to 0.50 mg Hg·L−1. For the same concentrations, the effect of contamination on the physiological condition of the plant was tested by observing changes in the presence of chlorosis and necrosis. Analysis of enzymatic activity using the API ZYM test for plants exposed to mercury did not show any significant changes. The phytoremediation process produces a significant amount of spent phytoremediation biomass containing large amounts of mercury. Sustainable management in the form of a mixture with soil substrate, uncontaminated with mercury, was proposed. Microtox toxicity analysis of water extracts from soil containing biomass, with a final mercury content in the substrate of 1 mg Hg·kg−1 of soil, showed no toxicity to the environment. However, microbiological analysis of the same soil substrate showed changes in the total number of bacteria, actinomycetes, fungi, moulds, and yeasts compared to the control samples.

A rapid and timely response to the impacts of mercury chloride, which is indispensable to the chemical industry, on aquatic organisms is of great significance. Here, we investigated whether the YOLOX (improvements to the YOLO series, forming a new high-performance detector) observation system can be used for the rapid detection of the response of Daphnia magna targets to mercury chloride stress. Thus, we used this system for the real-time tracking and observation of the multidimensional motional behavior of D. magna. The results obtained showed that the average velocity (v¯), average acceleration (a¯), and cumulative travel (L) values of D. magna exposed to mercury chloride stress changed significantly under different exposure times and concentrations. Further, we observed that v¯, a¯ and L values of D. magna could be used as indexes of toxicity response. Analysis also showed evident D. magna inhibition at exposure concentrations of 0.08 and 0.02 mg/L after exposure for 10 and 25 min, respectively. However, under 0.06 and 0.04 mg/L toxic stress, v¯ and L showed faster toxic response than a¯, and overall, v¯ was identified as the most sensitive index for the rapid detection of D. magna response to toxicity stress. Therefore, we provide a strategy for tracking the motile behavior of D. magna in response to toxic stress and lay the foundations for the comprehensive screening of toxicity in water based on motile behavior.

Acute and chronic exposure of heavy metals exerts detrimental effect at the cellular level and is a rising global concern. The pollutants once introduced in the water bodies, subsequently enters the food chain, and poses risks not only to the aquatic organisms, but to the human consumers as well. Therefore, understanding the toxicological level of these metals is vital for assessing the severity of potential risks. The study aimed to conduct a comparative analysis of the acute toxicity of mercury and cadmium on Channa punctatus through a 96-hour bioassay. It was carried out in a semi-static laboratory condition following the standard guidelines. The behavioural, and mortality response was recorded at the 24, 48, 72, and 96 h of exposure duration for both toxicants. The results demonstrated distinct differences in toxicity levels between mercury and cadmium. The 96h-LC50 value for cadmium was measured at 6.19 mg/l, while for mercury, it was significantly lower at 0.44 mg/l. It was revealed that even the trace concentration of metals can induce toxicity, if given for a prolonged period of time. Furthermore, the study observed heightened toxicity of mercury, exerting adverse effects at lower concentrations compared to cadmium within the same exposure duration.

This study aims to explore the potential health risks linked to four heavy metals/metalloids (Pb, Cd, As, Hg) present in four commercially important fish species (Scombromorus commerson, Pseudorhombus elevatus, Thunnus tonggol and Otolithes ruber) in the Persian Gulf. Metals in fish muscle tissue were analyzed via ICP-MS. The analysis revealed that Scombromorus commerson (except for Pb) and Thunnus tonggol (except for As) exhibited the highest and lowest contamination levels, respectively. The Hazard Index findings highlighted arsenic and mercury as the most hazardous elements. However, the Target Hazard Quotient values for each metal and fish species remained within safe thresholds. The highest and lowest Total Carcinogenic Risk was concerning Pseudorhombus elevates (As: 7.41-E05), and Thunnus thonggol (Pb: 3.21-E07), respectively. TCR analysis suggests that the cancer risk of studied metals was below the negligible level (TCR < 10-6) or within the acceptable level (10-6 < TCR < 10-4), potentially not posing carcinogenic risks through extended consumption.

The continuous fragmentation of plastics and release of synthetic nanoplastics from products have been aggravating nanoplastic pollution in the marine ecosystem. The carrier role of nanoplastics may increase the bioavailability and toxicity effects of toxic metals, e.g., mercury (Hg), which is of growing concern. Here, the copepod Tigriopus japonicus was exposed to polystyrene nanoplastics (PS NPs) and Hg (alone or combined) at environmental realistic concentrations for three generations (F0-F2). Then, Hg accumulation, physiological endpoints, and transcriptome were analyzed. The results showed that the copepod's reproduction was significantly inhibited under PS NPs or Hg exposure. The presence of PS NPs caused significantly higher Hg accumulation, lower survival, and lower offspring production in copepods relative to Hg exposure, suggesting an increased threat to the copepod's survivorship and health. From the molecular perspective, combined PS NPs and Hg caused a graver effect on the DNA replication, cell cycle, and reproduction pathways relative to Hg exposure, linking to lower levels of survivorship and reproduction. Taken together, this study provides an early warning of nanoplastic pollution for the marine ecosystem not only because of their adverse effect per se but also their carrier role for increasing Hg bioaccumulation and toxicity in copepods.

Mercury (Hg) is a global pollutant that affects numerous marine aquatic ecosystems. We isolated Chlorococcum dorsiventrale Ch-UB5 microalga from coastal areas of Tunisia suffering from metal pollution and analyzed its tolerance to Hg. This strain accumulated substantial amounts of Hg and was able to remove up to 95% of added metal after 24 and 72 h in axenic cultures. Mercury led to lesser biomass growth, higher cell aggregation, significant inhibition of photochemical activity, and appearance of oxidative stress and altered redox enzymatic activities, with proliferation of starch granules and neutral lipids vesicles. Such changes matched the biomolecular profile observed using Fourier Transformed Infrared spectroscopy, with remarkable spectral changes corresponding to lipids, proteins and carbohydrates. C. dorsiventrale accumulated the chloroplastic heat shock protein HSP70B and the autophagy-related ATG8 protein, probably to counteract the toxic effects of Hg. However, long-term treatments (72 h) usually resulted in poorer physiological and metabolic responses, associated with acute stress. C. dorsiventrale has potential use for Hg phycoremediation in marine ecosystems, with the ability to accumulating energetic reserves that could be used for biofuel production, supporting the notion of using of C. dorsiventrale for sustainable green chemistry in parallel to metal removal.

No abstract available

Mercury (Hg) is a global contaminant affecting aquatic ecosystems' health. Chronic exposure to Hg has shown that the normal development of zebrafish embryo-larvae is affected. However, the molecular mechanisms behind the toxicity of Hg on fish embryonic development are still poorly understood. This work aimed to investigate the effects of Hg exposure on zebrafish embryo-larvae using a combined approach at individual (mortality, embryo development and locomotor behavior) and biochemical (neurotoxicity and oxidative stress enzymatic activities and protein phosphatase expression) levels. The Fish Embryo Toxicity assay followed the Organization for Economic Cooperation and Development Guideline 236 and used a concentration range between 13 and 401 μg Hg/L. Lethal and developmental endpoints were examined at 24, 48, 72 and 96 hpf. Biochemical markers, including Acetylcholinesterase (AChE), Catalase (CAT), Glutathione Reductase (GR), and Glutathione-S-Transferase (GST) activities and, for the first time, the expression of the protein phosphatase 1 gamma (PP1γ) was assessed after 24, 48, 72 and 96 h of exposure to 10 and 100 μg Hg/L. The behavioral effects of a sublethal range of Hg (from 0.8 to 13 μg Hg/L) were assessed using an automated video tracking system at 120 hpf. Several developmental abnormalities on zebrafish embryos and larvae, including pericardial edema, spin and tail deformities and reduced rate of consumption of the yolk sac, were found after exposure to Hg (LC50 at 96 hpf of 139 μg Hg/L) with EC50 values for total malformations ranging from 22 to 264 μg Hg/L. After 96 hpf, no significant effects were observed in the CAT and GR activities. However, an increase in the GST activity in a concentration and time-dependent manner was found, denoting possible stress-related adaptation of zebrafish embryos to deleterious effects of Hg exposure. The AchE activity showed a response pattern in line with the behavioral responses. At the lowest concentration tested, no significant effects were found for the AChE activity, whereas a decrease in AChE activity was observed at 100 μg Hg/L, suggesting that exposure to Hg induced neurotoxic effects in zebrafish embryos which in turn may explain the lack of equilibrium found in this study (EC50 at 96 hpf of 83 μg Hg/L). Moreover, a decrease in the PP1γ expression was found after 96 h of exposure to 10 and 100 μg Hg/L. Thus, we suggest that Hg may be an inhibitor of PP1γ in zebrafish embryos-larvae and thus, along with the alterations in the enzymatic activity of GST, explain some of the developmental malformations observed, as well as the lack of equilibrium. Hence, in this study, we propose the use of PP1 expression, in combination with apical and biochemical endpoints, as a precursor for assessing Hg's toxic mechanism on embryonic development.

Mercury (Hg) is a global, persistent and inevitable pollutant, the toxicity of which is mostly reflected in its species including inorganic Hg (InHg) and methyl mercury (MeHg). Using diffusive gradients in thin films (DGT) is deemed as a reliable technique to determine the bioavailability of pollutants. This study is the first attempt to assess the integrated toxicity of mercury species mixtures in sediments to the aquatic biota based on the DGT technique. In the course, the Daya Bay under serious anthropogenic influences was selected as the study case. The results showed that the DGT concentrations of InHg and MeHg were detected as 0.30-1.93 μg/L and 0.28-1.94 μg/L respectively in the surface sediments collected from the Daya Bay. In terms of the toxicity of single mercury species, the risk quotient (RQ) values of InHg and MeHg significantly exceeded 1, indicating that the adverse effects of InHg and MeHg should not be ignored. In terms of the integrated toxicity of mercury species mixtures, the probabilistic biological risk assessment results demonstrate that Daya Bay features low (3.32%) probability of toxic effects in its surface sediments to the aquatic biota.

The growing use of plastics, including microplastics (MPs), has enhanced their potential release into aquatic environments, where microalgae represent the basis of food webs. Due to their physicochemical properties, MPs may act as carriers of organic and inorganic pollutants. The present study aimed to determine the toxicity of polyethylene MPs (plain and oxidized) and the model pollutants chlorpyrifos (CPF) and mercury (Hg) on the red microalgae Rhodomonas lens, to contribute to the understanding of the effects of MPs and associated pollutants on marine ecosystems, including the role of MPs as vectors of potentially harmful pollutants to marine food webs. R. lens cultures were exposed to MPs (1-1000 μg/L; 25-24,750 particles/mL), CPF (1-4900 μg/L), Hg (1-500 μg/L), and to CPF- and Hg-loaded MPs, for 96 h. Average specific growth rate (ASGR, day-1), cellular viability and pigment concentration (chlorophyll a, c2 and carotenoids) were measured at 48 and 96 h. No significant effects were observed on the growth pattern of the microalgae after 96-h exposure to plain and oxidized MPs. However, a significant increase in cell concentration was detected after 48-h exposure to plain MPs. A decrease of the ASGR was noticed after exposure to CPF, Hg and to CPF/Hg-loaded MPs, whereas viability was affected by exposure to MPs, CPF and Hg, alone and in combination. Chlorophyll a and c2 significantly decreased when microalgae were exposed to plain MPs and CPF, while both pigments significantly increased when exposed to CPF-loaded MPs. Similarly, chlorophyll and carotenoids content significantly decreased after exposure to Hg, whereas a significant increase in chlorophyll a was observed after 48-h exposure to Hg-loaded MPs, at the higher tested concentration. Overall, the presence of MPs modulates the toxicity of Hg and CPF to these microalgae, decreasing the toxic effects on R. lens, probably due to a lower bioavailability of the contaminants.

Mercury (Hg) is one of the most toxic pollutants to aquatic organisms. The influence of salinity on Hg toxicity, an important factor restricting the development of global marine aquatic life criteria (ALC), is unclear. Therefore, mercury toxicity data were corrected based on salinity using the aggregate slope method, and the ALC values were derived. Short-term aquatic life criteria (SALC) and long-term aquatic life criteria (LALC) were derived using the species sensitivity distribution method based on Log-logistic, Log-normal, Burr III, Gumbel, and Weibull models. The hazard quotient (HQ) and joint probability curve (JPC) methods were used to evaluate the ecological risk of Hg in the coastal waters of China. The results showed that the SALC and LALC of Hg in the coastal waters of China were 2.21 and 0.54 μg/L. The toxicity data and salinity were positively correlated for Chordate and Arthropoda and negatively correlated for Mollusca. The SALC values increased by approximately 75%, with salinities ranging from 10 to 20 ppt. A slight peak in the SALC at mid-salinities was also observed. The ecological risk assessment of Hg in China's coastal waters showed that attention should be paid to Hg pollution in the Bohai Sea and East China Sea, especially the ecological risk of Hg to crustacean organisms. This study could promote the development of water quality criteria for coastal waters and provide a technical reference for mercury management in the coastal waters of China.

No abstract available

Mercury (Hg) is an environmental pollutant that threatens aquatic life. Many environmental factors, including water temperature, are reported to influence the toxicity of dissolved chemicals in the aquatic ecosystem. Therefore, we investigated the impact of thermal stress on Hg-induced subchronic toxicity in Nile tilapia (Oreochromis niloticus). Fish were randomly allocated into five groups. Group I served as the control and kept at 25 °C. Groups II, III, IV, and V were reared at 25, 28, 31, and 34 °C, respectively, and co-exposed to HgCl2 (1/10 LC50) for 42 days. Blood and tissue samples were collected after 21 and 42 days. All HgCl2-exposed groups exhibited significant elevations in serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, and creatinine, along with decreases in the serum total protein and albumin. In addition, marked reductions in antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSPx), were observed. Remarkable increases in Hg tissue concentrations were detected along with increases in heat shock protein (HSP) 70 mRNA expression. Interestingly, the patterns data that were recorded were more coincident with the water temperature than the period of exposure. In conclusion, water temperature and exposure period are two crucial factors modulating HgCl2-induced toxicity and bioaccumulation in Nile tilapia. Our findings provide new insights concerning the impact of thermal stress as an environmental factor on Hg toxicity and bioaccumulation in Nile tilapia and, in turn, on fish and fish consumer health.

Mercury (Hg) has been increasing in waters, sediments, soils and air, as a result of natural events and anthropogenic activities. In aquatic environments, especially marine systems (estuaries and lagoons), Hg is easily bioavailable and accumulated by aquatic wildlife, namely bivalves, due to their lifestyle characteristics (sedentary and filter-feeding behavior). In recent years, different approaches have been developed with the objective of removing metal(loid)s from the water, including the employment of nanomaterials. However, coastal systems and marine organisms are not exclusively challenged by pollutants but also by climate changes such as progressive temperature increment. Therefore, the present study aimed to (i) evaluate the toxicity of remediated seawater, previously contaminated by Hg (50 mg/L) and decontaminated by the use of graphene-based nanomaterials (graphene oxide (GO) functionalized with polyethyleneimine, 10 mg/L), towards the mussel Mytilus galloprovincialis; (ii) assess the influence of temperature on the toxicity of decontaminated seawater. For this, alterations observed in mussels’ metabolic capacity, oxidative and neurotoxic status, as well as histopathological injuries in gills and digestive tubules were measured. This study demonstrated that mussels exposed to Hg contaminated seawater presented higher impacts than organisms under remediated seawater. When comparing the impacts at 21 °C (present study) and 17 °C (previously published data), organisms exposed to remediated seawater at a higher temperature presented higher injuries than organisms at 17 °C. These results indicate that predicted warming conditions may negatively affect effective remediation processes, with the increasing of temperature being responsible for changes in organisms’ sensitivity to pollutants or increasing pollutants toxicity.

Bacteria are the most abundant organisms on Earth and also the major life form affected by mercury (Hg) poisoning in aquatic and terrestrial food webs. In this study, we applied high energy-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy to bacteria with intracellular concentrations of Hg as low as 0.7 ng/mg (ppm) for identifying the intracellular molecular forms and trafficking pathways of Hg in bacteria at environmentally relevant concentrations. Gram-positive Bacillus subtilis and Gram-negative Escherichia coli were exposed to three Hg species: HgCl2, Hg-dicysteinate (Hg(Cys)2), and Hg-dithioglycolate (Hg(TGA)2). In all cases, Hg was transformed into new two- and four-coordinate cysteinate complexes, interpreted to be bound, respectively, to the consensus metal-binding CXXC motif and zinc finger domains of proteins, with glutathione acting as a transfer ligand. Replacement of zinc cofactors essential to gene regulatory proteins with Hg would inhibit vital functions such as DNA transcription and repair and is suggested to be a main cause of Hg genotoxicity.

No abstract available

Experiments examining mercury (Hg) toxicity in Daphnia are usually conducted in highly standardized conditions that prevent the formation of biofilm. Although such standardization has many advantages, extrapolation of results to natural conditions and inference of ecological effects is challenging. This is especially true since biofilms can accumulate metals/metalloids and play a key role in their transfer to higher trophic level organisms. In this study, we experimentally tested the effects of spontaneously appearing biofilm in Daphnia cultures on accumulation of Hg and its natural antagonist selenium (Se) in Daphnia magna. We added Hg (in the form of mercury (II) chloride) at two concentrations (0.2 µg/L and 2 µg/L) to experimental microcosms and measured the uptake of Hg and Se by D. magna in the presence and absence of biofilm. To test for consistent and replicable results, we ran two identical experimental sets one week apart. Biofilm presence significantly reduced the accumulation of Hg, while increasing the tissue Se content in D. magna, and these findings were reproducible across experimental sets. These findings indicate that highly standardized tests may not be adequate to predict the bioaccumulation and potential toxicity of metals/metalloids under natural conditions.

No abstract available

Water column hypoxia is a key process influencing methylmercury (MeHg) production and availability in waterbodies worldwide. During seasonal destratification, large, short-lived pulses of aqueous MeHg may be released into the subsequently mixed water column, but little is known about the fate of these pulses, particularly whether there are concomitant increases in MeHg uptake into aquatic food webs. We examined the magnitude and timing of MeHg uptake across several trophic guilds relative to the reservoir stratification status using biweekly mercury data from water, zooplankton, and fish (Bluegill, Lepomis macrochirus and Smallmouth Bass, Micropterus dolomieu). Zooplankton MeHg concentrations increased by up to 250% during destratification, concurrent with increases in aqueous MeHg concentrations. Zooplankton and filter-passing MeHg concentrations were positively correlated when the reservoir was mixed (R2 = 0.95) and destratifying (R2 = 0.57) but not while the reservoir was stratified (R2 = 0.21). Mercury concentrations in adult bluegill and juveniles of both fish species increased 20–70% following destratification, with responses lagging 4–8 weeks behind those in water and zooplankton MeHg. Mercury concentrations in piscivorous adult bass varied little over the course of the study. Our findings demonstrate the responsiveness of reservoir food webs to pulses in MeHg availability, suggesting that these pulses could play an important role in biotic MeHg exposure within and downstream of reservoirs.

New hydroelectric developments, built to meet rising energy demands, transform natural riverscapes into lentic-like reservoirs while flooding terrestrial systems. This has led to increased bacterial production of methylmercury (MeHg), a neurotoxin with high absorption and biomagnification potential, resulting in high concentrations in predatory fish. Still, lower trophic level processes governing this trophic increase, particularly zooplankton dynamics, are not well understood, hampering accurate predictions, especially for series of reservoirs along a river. We found that in a boreal multi-reservoir complex (Romaine River, QC), bulk zooplankton MeHg and total mercury (THg) bioaccumulation responded rapidly to upstream impoundments, with pronounced increases typically emerging the following year. Linear regression estimated MeHg increases of 25 to 63 ng⋅g-1⋅yr-1 in reservoirs (one run-of-river dam, two large reservoirs) and 43 ng⋅g-1⋅yr-1 downriver, highlighting their usefulness as indicators of short-term Hg dynamics. Synchronous year-to-year zooplankton MeHg and THg patterns across reservoirs and downriver suggested responses were driven by the timing of seasonal events (ice off, ecological succession), while transient variability between reservoir sub-environments led to higher baseline MeHg within warm, shallow bays. Dissolved MeHg (<0.45 μm) levels partially predicted (∼40%) zooplankton MeHg and THg concentrations and although high bioaccumulation factors (BAFs) indicated an efficient bioaccumulation by algae and zooplankton, BAFs declined with higher dissolved MeHg. Rises in temperature were associated with decreased Cladocera abundance, increased copepod growth, and reduced MeHg aqueous exposure and bioaccumulation levels later in summer. We propose a conceptual model of zooplankton MeHg dynamics in a boreal reservoir series following impoundment, offering valuable insights for environmental managers monitoring recently impounded multi-reservoir systems.

Though outbreaks of defoliating insects are a widespread, natural disturbance in Canadian boreal forests and their magnitude and duration are increasing in recent years, we have little understanding of the impacts on stream ecosystems. Herein we examined the fate of mercury (Hg), a toxic element affected by other landscape-scale forest disturbances, in twelve stream food webs in Gaspé Peninsula, Québec, Canada, that ranged in their severity of watershed defoliation from spruce budworm (Choristoneura fumiferana). Basal food sources (coarse and fine particulate organic matter, and biofilms), several macroinvertebrate taxa, and fish (brook trout [Salvelinus fontinalis] and slimy sculpin [Cottus cognatus]) were sampled in 2019 and 2020 and analyzed for stable isotopes of C and N, methylmercury (MeHg) or total Hg (THg, fish only). Hierarchical partitioning models were used to identify relative importance among landscape and local water quality variables, and they explained 76 and 65% of variation in brook trout THg and carnivorous invertebrate (Chloroperlidae, Rhyacophila, Parapsyche) MeHg levels, respectively, with dissolved organic carbon (DOC) as the main driver increasing biotic mercury levels. Trophic magnification slopes (TMS) (calculated as log10Hg vs. δ15N) ranged from 0.27-0.38 across all watersheds but were not related to defoliation severity or DOC concentrations. Collectively, these findings suggest that local measures of water quality are more important drivers of Hg bioaccumulation in stream biota than landscape disturbances caused by forest defoliation by spruce budworm.

Aquaculture organisms may accumulate metals to induce health risks. Compared with the focus on total contents, chemical-specific risk assessment makes reasonable but is rare. Herein, we elucidated occurrence of twelve metal compounds in shrimp and fish (edible muscle, one of major metal-containing and generally targeted organs), water, sediment, and feedstuff from two aquaculture ponds in Zhejiang Province (one of the major aquatic production and consumption areas). We detected Cd(II) (0.6 -71.4 μg kg-1 in 100 % prawn but 63 % fish), methylmercury (MeHg, 0.5 -7.1 μg kg-1 in 100 % fish but 61 % shrimp), Pb(II) (0.4 -1.0 μg kg-1 in 57 % fish and 39 % prawn), and trimethyltin and triethyltin (0.4 -0.7 μg kg-1), which were much lower than the maximum limits in China. Pb(II), Cd(II), and Hg(II) up to 0.38 mg kg-1 were main contaminants in sediment while Cd(II) and Pb(II) up to 0.44 mg kg-1 were major contaminants in feedstuff compared with Cd(II), Sn(II), Hg(II), and Pb(II) majored in water at ng L-1 levels. Ecological risks were low in water but high for tributyltin in sediment. Additionally, light bioaccumulation of Cd(II) from sediment for prawn and methylmercury from feedstuff/sediment for crucian and bighead carp was induced. We also found light health risk of triethyl- and trimethyl lead, and Cd(II) (to children) associated with fish/shrimp consumption (edible muscle). This study proved high necessity of chemical-specific assessment, and shall trigger increasing interest to more metallic compounds in a wide range of uncultured and cultured plants and animals.

Significance The interaction between climate change and methylmercury (MeHg) bioaccumulation poses significant challenges in assessing its impacts on food safety and human health. Our study explores this complex relationship, revealing that freshwater wild fish is an underappreciated dietary source of MeHg for Asian fish consumers, representing the world’s largest freshwater wild fish-consuming population. Our results suggest that the combined impacts of key climate factors will elevate MeHg exposure risks due to rising concentrations in freshwater wild fish, although warming temperatures alone may reduce MeHg accumulation. This climate-driven increase in MeHg bioaccumulation could jeopardize ongoing global efforts to mitigate human exposure under the United Nations Minamata Convention on Mercury, ultimately undermining progress toward sustainable development.

Mercury (Hg) contamination in marine ecosystems poses a significant environmental and health concern, particularly in Antarctica where data remain scarce. This study investigates total mercury (THg) and methylmercury (MeHg) concentrations in muscle tissues of Notothenia coriiceps from Admiralty Bay (King George Island, Antarctica) to investigate bioaccumulation patterns and ecological drivers. Stable isotope analyses of carbon (δ13C) and nitrogen (δ15N) were used to determine trophic positioning and dietary sources and selenium (Se) concentrations and Se:Hg molar ratios were measured to assess potential detoxification. THg in N. coriiceps ranged from 100.2 to 670.3 ng/g d.w., with MeHg comprising approximately 79% of THg. A strong positive correlation between both THg and MeHg and δ15N confirmed trophic biomagnification (TMS = 0.22 for THg, 0.18 for MeHg), with a 1.6-1.8-fold increase in mercury concentration per trophic level. Notably, considerable inter-individual variability in Hg burdens was observed, particularly among the smallest individuals, which exhibited relatively high THg concentration despite their diminutive size. This counterintuitive pattern likely reflects diet, foraging habitat, and trophic ecology appears to overshadow body size alone in determining Hg accumulation. All studied fish had Se:Hg ratios >1, suggesting mitigated toxicity. This study provides critical data on mercury bioaccumulation and biomagnification in Antarctic fish, emphasizing the necessity for continued monitoring of Hg contamination in polar marine ecosystems.

Mercury concentrations in the Laurentian Great Lakes waters are among the lowest reported in the literature, while game fish concentrations approach consumption advisory limits, particularly in Lakes Superior, Huron, and Michigan, indicating efficient methylmercury transfer from water to game fish. To determine if increased transfer efficiency is evident within the lower food web, we measured (2010-2018) mercury and dissolved organic carbon (DOC) in water, and in size-sieved seston, dietary tracers (carbon and nitrogen isotope ratios), phytoplankton methylmercury bioaccumulation, and methylmercury biomagnification between increasing seston size fractions. We observed consistently low filter-passing methylmercury (<0.010 ng L-1) and comparatively variable DOC (1.1 to 3.4 mg L-1) concentrations. Methylmercury biomagnification factors between size-sieved seston were similar between lakes. Bioaccumulation factors in phytoplankton were among the highest in the literature (log 5.5 to 6.1), exceeding those in oceans, smaller lakes, and streams, and was influenced by DOC. Higher bioaccumulation rates increase the susceptibility of methylmercury accumulation into the food web. Because mercury is dominantly delivered to the Great Lakes through the atmosphere and the biota therein is highly susceptible to methylmercury uptake, we propose that the Laurentian Great Lakes are excellent sentinels to trace the success of efforts to decrease global mercury emissions (e.g., Minamata Treaty) in the future.

High levels of methylmercury (MeHg) have been reported in Arctic marine biota, posing health risks to wildlife and human beings. Although MeHg concentrations of some Arctic species have been monitored for decades, the key environmental and ecological factors driving temporal trends of MeHg are largely unclear. We develop an ecosystem-based MeHg bioaccumulation model for the Beaufort Sea shelf (BSS) using the Ecotracer module of Ecopath with Ecosim, and apply the model to explore how MeHg toxicokinetics and food web trophodynamics affect bioaccumulation in the BSS food web. We show that a food web model with complex trophodynamics and relatively simple MeHg model parametrization can capture the observed biomagnification pattern of the BSS. While both benthic and pelagic production are important for transferring MeHg to fish and marine mammals, simulations suggest that benthic organisms are primarily responsible for driving the high trophic magnification factor in the BSS. We illustrate ways of combining empirical observations and modelling experiments to generate hypotheses about factors affecting food web bioaccumulation, including the MeHg elimination rate, trophodynamics, and species migration behavior. The results indicate that population dynamics rather than MeHg elimination may determine population-wide concentrations for fish and lower trophic level organisms, and cause large differences in concentrations between species at similar trophic levels. This research presents a new tool and lays the groundwork for future research to assess the pathways of global environmental changes in MeHg bioaccumulation in Arctic ecosystems in the past and the future.

Thermal stratification of reservoirs can lead to anaerobic conditions that facilitate the microbial conversion of mercury (Hg) to neurotoxic and bioaccumulative methylmercury (MeHg). But MeHg production is just the first step in a complex set of processes that affect MeHg in fish. Of particular relevance is uptake into suspended particulate matter (SPM) and zooplankton at the base of the pelagic food web. We assessed plankton dynamics and Hg uptake into the pelagic food web of four Hg-impaired California water reservoirs. Combining water chemistry, plankton taxonomy, and stable carbon (C) and nitrogen (N) isotope values of SPM and zooplankton samples, we investigated differences among the reservoirs that may contribute to differing patterns in MeHg bioaccumulation. Methylmercury accumulated in SPM during the spring and summer seasons. Percent MeHg (MeHg/Hg*100%) in SPM was negatively associated with δ15N values, suggesting that “fresh” algal biomass could support the production and bioaccumulation of MeHg. Zooplankton δ13C values were correlated with SPM δ13C values in the epilimnion, suggesting that zooplankton primarily feed in surface waters. However, zooplankton MeHg was poorly associated with MeHg in SPM. Our results demonstrate seasonal patterns in biological MeHg uptake and how multiple data sources can help constrain the drivers of MeHg bioaccumulation.

The four largest freshwater lakes in southwestern France are of both ecological and economic importance. However, some of them are subjected to mercury (Hg) contamination, resulting in the ban of human consumption of piscivorous fish. Moreover, beyond predatory fish, little information exist regarding Hg levels in other species of these ecosystems. In this context, we used a food web analytical approach to investigate Hg bioaccumulation and biomagnification in relation to the trophic structure of these four lakes. More specifically, various organisms (macrophytes, epiphyton, invertebrates and fish) were collected at the four lakes and analysed for carbon and nitrogen stable isotopes as well as for total Hg (THg) and methylmercury (MeHg). A spatial variability of bioaccumulation in organisms was observed, particularly in carnivorous fish, with higher Hg levels being found in the two more northern lakes (median±SE: 3491 ± 474 and 1113 ± 209 ng THg.g-1 dw in lakes HC and L, respectively) than in the southern pair (600 ± 117 and 911 ± 117 ng THg.g-1 dw in lakes CS and PB, respectively). Methylmercury biomagnification was observed through the food webs of all four lakes, with different trophic magnification slopes (HC = 0.16; L = 0.33; CS = 0.27; PB = 0.27), even though the length of the food chains was similar between the lakes. Our results suggest that rather than the food web structure, anthropogenic inputs (sulfate in northern lakes and phosphorus inputs in southern ones) may have a strong impact, more or less directly, on Hg methylation in freshwater environments, and lead to concentrations exceeding environmental recommendations despite low Hg backgrounds in sediment and water.

Estuarine systems have received ongoing mercury (Hg) inputs from both point sources and regional contamination and have high legacy Hg in sediments. This is an environmental concern given that coastal seafood is an important vector for human exposure to methylmercury (MeHg). The base of the food chain represents the most important trophic steps for MeHg bioaccumulation. The magnitude of the uptake by phytoplankton, and their consumers, is influenced by many factors, in addition to sediment and water MeHg concentrations that impact MeHg assimilation into phytoplankton and the trophic transfer to higher trophic levels, both benthic and pelagic. For forage fish, such as mummichogs (Fundulus heteroclitus), abiotic and biotic (bioenergetic) factors can influence their MeHg content, and diet is also important as they feed both on benthic and pelagic prey. Given that the importance of sediment MeHg versus pelagic MeHg sources has been debated, we updated a phytoplankton bioaccumulation model, and coupled this with a bioaccumulation model for MeHg concentration in mummichog tissue to examine the controlling factors for sites, from Maine to Maryland, ranging widely in their Hg concentrations and other variables. The study highlighted the importance of DOC in modulating uptake into the pelagic food web, but also demonstrated the importance of diet in controlling mummichog MeHg. Finally, the relative importance of MeHg source - sediment or water column - was correlated with the level of Hg contamination. Sediment-derived MeHg was a more important source for highly Hg contaminated systems. As water column and sediment MeHg are not strongly correlated for the studied ecosystems, their importance as a source of MeHg to mummichogs varies with location. The study highlights the differences across ecosystems in MeHg bioaccumulation pathways, and that uptake into phytoplankton is an important variable controlling forage fish concentration.

Mercury (Hg) is a global contaminant that poses a human health risk in its organic form, methylmercury (MeHg), through consumption of fish and fishery products. Bioaccumulation of Hg in the aquatic environment is controlled by a number of factors expected to be altered by climate change. We examined the individual and combined effects of temperature, sediment organic carbon, and salinity on the bioaccumulation of MeHg in an estuarine amphipod, Leptocheirus plumulosus, when exposed to sediment from two locations in the Gulf of Maine (Kittery and Bass Harbor) that contained different levels of MeHg and organic carbon. Higher temperatures and lower organic carbon levels individually increased uptake of MeHg by L. plumulosus as measured by the biota-sediment accumulation factor (BSAF), while the effect of salinity on BSAF differed by sediment source. Multi-factor statistical modeling using all data revealed a significant interaction between temperature and organic carbon for both sediments, in which increased temperature had a negative effect on BSAF at the lowest carbon levels and a positive effect at higher levels. Our results suggest that increased temperature and carbon loading, of a magnitude expected as a result from climate change, could be associated with a net decrease in amphipod BSAF of 50 to 71%, depending on sediment characteristics. While these are only first-order projections, our results indicate that the future fate of MeHg in marine food webs is likely to depend on a number of factors beyond Hg loading.

Differences in sediment biogeochemistry among tidal marsh features with different hydrological and geomorphological characteristics, including marsh interiors, marsh edges, first-order channels, and third-order channels, can result in spatial variation in MeHg production and availability. To better understand the link between MeHg production in sediments and bioaccumulation in primary and secondary consumer invertebrates and fish, we characterized mesoscale spatial variation in sediment biogeochemistry and MeHg concentrations of sediments, water, and consumer tissues among marsh features. Our results indicated that marsh interiors had biogeochemical conditions, including greater concentrations of organic matter and sulfate reduction rates, that resulted in greater MeHg concentrations in sediments and surface water particulates from marsh interiors compared to other features. Tissue MeHg concentrations of consumers also differed among features, with greater concentrations from marsh edges and interiors compared to channels. This spatial mismatch of MeHg concentrations in sediments and water compared to those in consumers may have resulted from differences in behavior and physiology among consumers that influenced the spatial scale over which MeHg was integrated into tissues. Our results highlight the importance of sampling across a suite of marsh features and considering the behavioral and physiological traits of sentinel taxa for contaminant monitoring studies.

Mercury (Hg) bioaccumulation in freshwater fish represents a major pathway of human exposure, particularly in cascade reservoir systems where hydrological retention and legacy contamination can enhance methylmercury (MeHg) formation and trophic transfer. This study quantified total mercury (THg) concentrations in seven tissues of seven fish species from the Arda River cascade (Bulgaria). Multi-tissue measurements were integrated with morphometric predictors, multivariate statistical analyses, and combined deterministic and probabilistic human-health risk assessments. Muscle and liver contained the highest THg concentrations, whereas gills and gonads exhibited the lowest levels. Predatory species and larger individuals accumulated significantly more Hg, reflecting trophic magnification and size-dependent exposure. A longitudinal gradient across the cascade reservoirs suggests hydrological retention effects influencing mercury distribution. Species- and tissue-specific size–Hg relationships further indicate heterogeneous bioaccumulation dynamics among taxa. Risk assessment indicated acceptable exposure for adults and pregnant women at average consumption (140 g·week−1), but elevated exposure for children consuming high-Hg predators. Monte Carlo simulations (N = 30,000) revealed upper-tail risks, while Safe Weekly Intake thresholds provided species-specific consumption limits. These findings highlight the value of integrating multi-tissue monitoring with probabilistic risk modelling to support evidence-based fish-consumption advisories in contaminated freshwater systems.

Mercury (Hg) biotransformation can significantly affect the Hg speciation and bioaccumulation in fish, where gut microbiota play an important role in this process. Antibiotics have been extensively used in aquaculture and can affect gut microbial structure. However, the influence of antibiotics on Hg biotransformation in fish has not been thoroughly understood. The present study investigated the effects of antibiotic (florfenicol) application on gut microbiota and subsequent impacts on Hg biotransformation and bioaccumulation in tilapia (Oreochromis mossambicus). The results showed that the florfenicol treatment did not affect IHg accumulation in the IHg-exposed fish or the MeHg accumulation in the MeHg-exposed fish. However, methylation was significantly weakened (from 0.015% d-1 to 0.005% d-1) and demethylation was completely terminated (from 0.046% d-1 to non-observable level) in the florfenicol-treated fish as compared to the control fish. This can be ascribed to the major shift in the richness of microbial methylators/demethylators in fish gut. Furthermore, florfenicol disturbed the homeostasis of gut microbiome and enhanced the growth of opportunistic pathogens. Our results strongly suggested that antibiotic application significantly altered the gut microbial community, thereby increasing the potential of MeHg accumulation by fish. This study highlights the importance of appropriate use of antibiotics in aquaculture as well as decreasing the environmental risks of Hg contamination in fish.

This study investigated the contents of total mercury (THg), methylmercury (MeHg) and selenium (Se) in 22 fish species and 10 invertebrate species from the coastal East China Sea. The THg and MeHg contents were significantly higher in benthic fishes. Both Hg and Se biomagnified in the food webs, with evidences of associations during trophic transfer. In addition, Se:Hg molar ratio and Se health benefit value (HBVSe) were used as novel criteria for Hg exposure risk assessments, showing that Se presented in molar excess of Hg in all samples, which would negate the risks of Hg toxicity. HBVSe provided more informative results than Se:Hg molar ratio, pointing to possibly lower health risks for some fishes containing high levels of Hg and Se. Although the HBVSe results challenge the traditional Hg health risk assessment, its future application still requires worldwide comprehensive investigations.

Simple Summary The head kidney was primary organ that accumulated methylmercury in hybrid grouper. Muscle tissue had lower methylmercury content than the head kidney and liver. Nonspecific immune responses and bioaccumulation of methylmercury were linked to hybrid grouper health. Abstract Mercury (Hg) is a dangerous heavy metal that can accumulate in fish and is harmful when consumed by humans. This study investigated the bioaccumulation of mercury in the form of methylmercury (MeHg) and evaluated nonspecific immune responses such as phagocytic activity and superoxide anion (O2−) production in hybrid grouper (Epinephelus fuscoguttatus × E. lanceolatus). The hybrid grouper leukocytes were incubated with methylmercury chloride (CH3HgCl) at concentrations of 10–10,000 µg/L to determine cell viability, phagocytic activity, and O2− production in vitro. Subsequently, the grouper were exposed daily to CH3HgCl mixed in the experimental diets at concentrations of 0, 1, 5, and 10 mg/kg for 28 days. The bioaccumulation of MeHg in the liver, head kidney, and muscle tissue was measured, and the phagocytic activity and O2− production were evaluated. In vitro results indicated that cell viability was significantly lower than that of the control group at concentrations > 500 µg/L. The phagocytic rate and O2− production at concentrations ˃ 500 and ˃ 200 µg/L, respectively, were significantly lower than those of the control group. The dietary exposure demonstrated that MeHg accumulated more substantially in the liver and head kidney compared with the muscle tissue in the treatment groups. Moreover, the cumulative concentration significantly increased with higher concentrations and more days of exposure. The phagocytic rate and O2− production in the treatment groups were significantly lower than those in the control group from days 2 and 1, respectively. In conclusion, hybrid grouper accumulated significant MeHg in the liver and head kidney compared with the muscle tissue, and higher concentrations and more exposure days resulted in decreased cell viability, phagocytic activity, and O2− production.

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Bioaccumulation of mercury in freshwater fish is a complex process driven by environmental and biological factors. In this study, we assessed mercury in fish from four tributaries to the Red Deer River, Alberta, Canada, which are characterized by high surface water mercury concentrations. We used carbon (δ13C) and nitrogen (δ15N) stable isotopes to examine relationships between fish total mercury (THg) concentrations, food web dynamics and patterns in unfiltered THg and methylmercury (MeHg) concentrations. We found that THg concentrations exceeded the tissue residue quality guideline for the protection of wildlife consumers in 99.7% of fish sampled. However, while the surface water THg concentration was highest in Michichi Creek and the MeHg concentration was consistent across streams, patterns of fish THg concentrations varied depending on species. Furthermore, body size and trophic level were only correlated with THg concentrations in white sucker (Catostomus commersoni) and Prussian carp (Carrasius gibelio). The results of this study suggest that mercury poses a risk to the health of piscivorous wildlife in the Red Deer River watershed. Despite high THg concentrations in these streams, mercury bioaccumulation is not driven by environmental inorganic mercury concentrations. Additionally, commonly cited factors associated with mercury concentrations in fish, such as body size and trophic level, may not strongly influence bioaccumulation in these stream ecosystems.

High concentrations of mercury (Hg) have been documented in deep-water fish species from some Norwegian fjords. In this study, tusk (Brosme brosme) was sampled from four locations in the innermost parts of Sognefjorden in Western Norway. Total Hg and methylmercury (MeHg) levels were measured in liver tissue. To search for potential sublethal effects of Hg, we characterized the hepatic transcriptome in tusk with high and low levels of Hg bioaccumulation using global transcriptomics analysis (RNA-seq). The results showed that there was a significant correlation between fish weight and accumulated concentrations of MeHg but not total Hg. MeHg accounted for 30-40% of total Hg in liver of most of the fish, although at concentrations above 2-3 mg Hg/kg wet weight the percentage of MeHg dropped considerably. Transcriptome analysis resulted in hundreds of differentially expressed genes in the liver of tusk with high Hg levels. Functional enrichment analysis suggested that the top affected pathways are associated with protein folding, adipogenesis, notch signaling, and lipid metabolism (beta-oxidation and phospholipids). Based on transcriptional responses pointing to well-known effects of Hg compounds in fish, the study suggests that tusk in Sognefjorden could be negatively impacted by Hg bioaccumulation.

Large marine predators exhibit high concentrations of mercury (Hg) as neurotoxic methylmercury, and the potential impacts of global change on Hg contamination in these species remain highly debated. Current contaminant model predictions do not account for intraspecific variability in Hg exposure and may fail to reflect the diversity of future Hg levels among conspecific populations or individuals, especially for top predators displaying a wide range of ecological traits. Here, we used Hg isotopic compositions to show that Hg exposure sources varied significantly between and within three populations of white sharks (Carcharodon carcharias) with contrasting ecology: the north-eastern Pacific, eastern Australasian, and south-western Australasian populations. Through Δ200Hg signatures in shark tissues, we found that atmospheric Hg deposition pathways to the marine environment differed between coastal and offshore habitats. Discrepancies in δ202Hg and Δ199Hg signatures among white sharks provided evidence for intraspecific exposure to distinct sources of marine methylmercury, attributed to population and ontogenetic shifts in foraging habitat and prey composition. We finally observed a strong divergence in Hg accumulation rates between populations, leading to three times higher Hg concentrations in large Australasian sharks compared to north-eastern Pacific sharks, and likely due to different trophic strategies adopted by adult sharks across populations. This study illustrates the variety of Hg exposure sources and bioaccumulation patterns that can be found within a single species and suggests that intraspecific variability needs to be considered when assessing future trajectories of Hg levels in marine predators.

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This study proposes a pro-active approach for evaluations of methylmercury (MeHg), total mercury (THg), arsenic (As), cadmium (Cd) and lead (Pb) in situ bioaccumulation in fish (Atherinella brasiliensis) muscles, using specimens from the external sector of Guanabara Bay as a study case. This approach included an hierarchical sequence: analysis of the pollutants concentrations and their comparison to safety criteria; correlations between specimens concentrations vs length (as a proxy of exposure time); projections of concentrations in key lengths (sexual maturation, asymptotic, length limits for fishing and median of fish population) through polynomial regressions, dose-response analysis (Probit), decreasing curves and incorporation rates (using only three length intervals). The incorporation rates were ascending for MeHg and THg (continued bioaccumulation) and descending for As, Pb and Cd (possible biological dilution). The projections were satisfactory, evidencing their use for an improvement on the risks monitoring of fishing and fish consumption by humans in coastal environments.

Artisanal and small-scale gold mining (ASGM) activities are an important source of mercury (Hg) to the atmosphere globally, and in most countries in West Africa, where gold production has increased dramatically in the last decade from both commercial and ASGM activities. This study focused on examining the concentrations of Hg and methylmercury (MeHg) in water, sediments and fish in four regions associated with gold mining activities in Cote d'Ivoire to assess the potential exposure of the local communities to MeHg from fish consumption. Concentrations of dissolved total Hg and MeHg in water and sediment were elevated at some locations sample and were indicative of local contamination. Several locations had sediment total Hg above 100 ng g-1 and sediment %MeHg ranged from 0.03 to 4.4%. Fish concentrations exceeded 0.3 μg/ g wet wt., especially for carnivores and fish caught in the western region of the country. Bioaccumulation factors, relative to dissolved MeHg, were higher for carnivores than omnivores and varied with region, suggesting other factors besides MeHg concentration alone were impacting uptake and trophic transfer. Given that people in Cote d'Ivoire consume fish at a higher level than other countries, the levels in fish were sufficient to exceed the US EPA's guidance criteria even at average consumption levels, and particularly for people consuming fish at a higher rate. Overall, this study provides compelling evidence that ASGM activities in Cote d'Ivoire are leading to elevated exposure and likely impacting the health of the local populations in regions where such activity is occurring.

Methylmercury (MeHg) is a contaminant of global concern that bioaccumulates and bioamagnifies in marine food webs. Lower trophic level fauna are important conduits of MeHg from sediment and water to estuarine and coastal fish harvested for human consumption. However, the sources and pathways of MeHg to these coastal fisheries are poorly known particularly the potential for transfer of MeHg from the sediment to biotic compartments. Across a broad gradient of human land impacts, we analyzed MeHg concentrations in food webs at ten estuarine sites in the Northeast US (from the Hackensack Meadowlands, NJ to the Gulf of Maine). MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides). Moreover, MeHg concentrations were higher in pelagic fauna than in benthic-feeding fauna suggesting that MeHg delivery to the water column from methylation sites from within or outside of the estuary may be an important driver of MeHg bioaccumulation in estuarine pelagic food webs. In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms. Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish. Thus, even in systems with contaminated sediments, transfer of MeHg into estuarine food webs maybe driven more by the efficiency of processes that determine MeHg input and bioavailability in the water column.

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As a global toxic pollutant, mercury (Hg) bioaccumulation within food chain could be influenced by human disturbance. Ten typical fish species were collected from Changshou Lake, an artificial lake used to carry out cage fish culture, to investigate the C/N isotopic compositions and Hg bioaccumulation in fish. The results showed that the total Hg (THg) and methylmercury (MeHg) levels in fish muscles ((56.03 ± 43.96) and (32.35 ± 29.57) ng/g, wet weight), comparable with those in most studies in China, were significantly lower than the international marketing limit (0.5 mg/kg). Past human input for cage culture in this lake led to abnormal 15N enrichment in food chain, as the quantitative trophic levels based on δ15N were different with that classified by feeding behaviors. This phenomenon subsequently demonstrated that it should be considered thoughtfully with respect to the application of the traditional method for understanding Hg bioaccumulation power by the slope of log10[Hg] with δ15N regression in specific water body (i.e., Changshou Lake). In addition, no significant linear correlation between Hg and body weight or length of some fish species was observed, suggesting that the fish growth in the eutrophic environment was disproportionate with Hg bioaccumulation, and fish length or weight was not the main factor affecting Hg transfer with food web. The occurrence of human disturbance in aquatic system presents a challenge to a better understanding of the Hg bioaccumulation and biomagnification within the food chain.

This data article includes information on the impact of gold mining along five zones of a tropical river in the Pacific region of Colombia. The concentrations of total mercury (THg), total length, mertimercury (MeHg) were determined in 16 species of fish. With this information, it was shown as the concentrations of mercury in fish are influenced by the distribution in the contamination along the Atrato River Basin [1]. Further, THg and MeHg concentrations were related with the trophic level to show biomagnification, and with total length to show bioaccumulation, which is important to establish the potential risk to the environment and also to the health of the inhabitants living along the basin from the consumption of fish.

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Newly constructed reservoirs were recognized as hotspot of mercury (Hg) methylation, and then methylmercury (MeHg) accumulation in food chains. The risk of elevated MeHg concentrations in fish is one of the most important concerns in newly constructed reservoirs. The Three Gorges Reservoir (TGR) is one of the largest reservoirs in the world. However, the distribution and bioaccumulation characteristics of Hg species within the food chains and its potential ecological risk in the TGR remain poorly understood. In this study, 264 fish individuals covering 18 species were collected from the TGR. Total mercury (THg) and MeHg concentrations in different organs (gill, heart, liver, muscle and swim bladder) of fish species were analyzed; the values of δ13C and δ15N in fish muscle were determined as well to reveal the biomagnification properties of Hg in food chains. Our results showed that concentrations of THg (0.5-272 ng g-1, w.w.) and MeHg (0.1-199 ng g-1, w.w.) in fish muscle from the TGR ubiquitously fall below the safe fish consumption limit on Hg recommended by WHO (500 ng g-1, w.w.) and the US-EPA Water Quality Criterion for MeHg (300 ng g-1, w.w.). The short food web jointly with the limited trophic magnification factor in the TGR explained the relatively low Hg concentrations in predators. Among the five fish organs, muscle represented the highest Hg concentrations, followed by heart, liver, swim bladder, and gill, suggesting that muscle has the highest ability to accumulate Hg compared to the other organs. More importantly, no discernible "reservoir effect" was observed in the TGR within the initial few years after impoundment due to its special eco-environment including: 1) neutral and slightly alkaline pH and low dissolved organic carbon of water, 2) less vegetation coverage in inundated areas, 3) simple food web.

Mercury still represents one of the most hazardous threats for the aquatic ecosystem due to its high toxicity, and the fact that it can be easily incorporated into the food chain by accumulation in fish as MeHg. On the other hand, selenium is a micronutrient that is part of different antioxidant enzymes that regulate the cellular redox state, and whose complex interaction with Hg has been extensively studied from a toxicological point of view. In order to evaluate the protective effect of Se(IV) co-administration against MeHg accumulation and toxicity, we have selected an in-vivo model at two developmental stages: zebrafish eleutheroembryos and adult fish. Embryos were exposed during 48 h to MeHg (5 or 25 μg/l) and a concentration of Se (IV) representing a molar ratio close to one (2.5 or 12.5 μg/l), while adult zebrafish were exposed during 72 h to either 25 μg/l of MeHg alone or co-exposed with 12.5 μg/l of Se (IV). A significant decrease in MeHg bioaccumulation factor was observed in eleutheroembryos co-exposed to Se(IV). A time-dependent accumulation of MeHg was observed in all the analyzed organs and tissues of adult fish, which was significantly reduced in the muscular tissue and the intestine by Se(IV) co-administration. However, such protection against MeHg bioaccumulation was not maintained in the brain and liver. The data derived from the gene expression analysis also demonstrated the protective effect of Se(IV) against MeHg-induced oxidative stress and the activation of different defense mechanisms by Se(IV) co-administration.

Bioaccumulation of mercury and methylmercury in fish represents a serious risk to human beings. Extreme climate events like droughts may increase the trophic transfer of contaminants and net methylation of mercury. The present study assessed the influence of the 2014 drought on total mercury and methylmercury levels in fish from the lower Paraiba do Sul river basin. Contaminant levels were compared for Pimelodus fur, Pachyurus adspersus, Pimelodella lateristriga, Oligosarcus hepsetus, and Crenicichla lacustris captured in five sites in 2013 (N = 212) and 2014 (N = 231). The results indicate that levels of contaminants were higher during the drought in most species. Rainfall was weakly and negatively correlated with total mercury levels in most of the species. The weak relationship between these two variables was due to the indirect influence of rainfall on mercury bioaccumulation. In summary, drought increased the levels of two contaminants in fish.

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This research aimed to determine the pollution resources and the main parameters affecting the Aras River water quality, as one of the important rivers of the Caspian Sea watershed, within the borders of Iran, and to present control solutions. Hence, canonical correlation analysis (CCA) and principal component analysis (PCA) were used to reduce data dimensions and determine the pollution criteria based on four physical and six chemical parameters premeasured at 19 stations between 2020 and 2022. The CCA results showed that pH and dissolved oxygen (as physical variables) and also mercury, nitrate, and sulfate (as chemical variables) had a significant role in predicting the canonical variables of chemical and physical parameters, respectively. These pollutants predominantly originated from anthropogenic pollution sources, including runoff infiltration from surrounding vast agricultural lands (based on the first principle component results accounted for 39.3% of the variations), and also the soil erosion in the watershed (based on the second principle component results accounted for 25.7% of the variations). To conclude, the Aras River water quality management programs should focus more on controlling anthropogenic pollution sources to monitor the status of effective physicochemical parameters using multivariate statistical methods, especially CCA and PCA methods.

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This study examines the mercury content in the marine matrices water column, surface sediment and benthic invertebrates of Coronel and Coliumo bays, central Chile, under winter and summer conditions. Coronel Bay has been subject to intense industrialization in the last three decades, while Coliumo Bay remains as a fisherman's cove and a popular summer tourism destination. Our results reveal significantly higher mercury concentrations in the three environmental matrices analyzed for Coronel Bay, while Coliumo Bay exhibits levels within the range considered natural. Moreover, the mercury levels in Coronel Bay exceed the optimal criteria for aquatic life, indicating a deterioration in environmental quality of this locality. Industrial development is identified as main factor explaining the differences observed between these two coastal water bodies. This study presents the most updated record of mercury levels in the Southeast Pacific and represents the first comprehensive evaluation of marine environmental matrices in two bays with divergent activities.

Mining activity drives economic development and has established itself as one of the main industrial spheres globally. However, illegal, and artisanal gold mining, which uses mercury (Hg), is a major source of global pollution. Hg is highly toxic and persistent in the environment, affecting human health and the ecosystem. The objective of this research is to; (a) analyze Hg concentrations in surface waters of nine provinces of the Andean region of Ecuador and compare them with the maximum permissible limits of Ecuadorian regulations, and (b) evaluate the health risk of people exposed to waters with high Hg content through residential and recreational scenarios. In this study, 147 water samples from rivers and streams were analyzed. The results revealed worrying levels of Hg, especially in the provinces of Azuay and Loja where Hg values of up to 0.0913 mg/L and 0.0387 mg/L, respectively, were detected. In addition, it was found that all water samples did not meet the water quality criteria for the preservation of aquatic life, which represents a severe risk to the ecosystem. The probabilistic risk analysis yielded values that exceeded the acceptable exposure limit for adults and children in residential settings in Azuay and Loja, while in the recreational scenario the safe exposure limit was exceeded for both receptors only in the province of Azuay. The elevated presence of Hg in the provinces, mainly in Azuay and Loja, possibly related to illegal gold mining activity, represents a threat to water quality and aquatic life in the Andean region of Ecuador. Children are especially vulnerable, and effective regulation is required to ensure the safety of the population. This study provides valuable information for decision makers regarding the risk associated with Hg exposure in areas of mining activity in the Ecuadorian Andean region. In addition, it can contribute to the development of policies and strategies to control contamination in mining environments and protect human and environmental health in the region.

Enterobacteriaceae are Gram-negative bacteria that have many mechanisms to survive in contaminated environments. Klebsiella pneumoniae is one of them that express efflux pump genes in the presence of heavy metals, like AcrAb and OqxA genes. The purpose of this study is to investigate the relationship between the existence of efflux pump genes in K. pneumoniae, and heavy metal contamination in the Tigris River. By comparing important indicators to World Health Organization (WHO) criteria, this study aims to analyze the river's water quality. It focuses on detection of cadmium (Cd), lead (Pb), nickel (Ni), arsenic (As), mercury (Hg), iron (Fe), and cobalt (Co). Fifteen samples of the Tigris River near the Al-Dura project of water remediation were obtained and cultured on selective media, and the water quality parameters, like TSS, TDS, TH, pH, turbidity, EC, BOD, COD, OD, TOC, and heavy metals, were estimated. Bacterial DNA was extracted, then efflux genes were detected with the presence of heavy metals in the tested samples. Results illustrated that K. pneumoniae gave positive results in nine of the total fifteen samples, and the water quality parameters were within the normal ranges, except for elevated levels of DO and TOC, and decreased levels of BOD and COD, with a significant relationship among heavy metal levels with both AcrAB and OqxA genes at a significance level of p ≤ 0.05.

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The state of positive health and wellbeing is impossible without safe water. This study was aimed to assess the quality of Dilla town water sources. A total of 108 water samples were collected from twelve sites and selected physical and chemical parameters were analyzed. Most of the physicochemical parameters were in the acceptable range for water quality of WHO and CES. Three sampling sites were contaminated by nitrate with concentration range 51.68–126.30 mg/L. The heavy metal analysis indicated that, the level of iron, zinc, manganese, and chromium in some of the sites exceed values of WHO standard concentrations in the range 0.506–5.773, 3.606–4.312, 0.194–0.588 and 0.053–0.098 mg/L respectively. While three heavy metals (mercury, arsenic and lead) were above the WHO limit in all the sites. The bacteriological analysis of all the water sources indicated microbial contamination, total count of the coliforms ranging from 3 to 80 MPN/100 mL. As per WHO criteria, some of the water sources were grouped in to high-risk. The cause of such contamination may be due to no treatment or poor processing system. Therefore, the need to Hygiene promotion programs, urgent and continuous monitoring is highly recommended.

Fish contaminant studies with human health protection objectives typically focus on muscle tissue, recognizing that fillets are the commonly consumed tissue fraction. Muscle biopsy punch sampling for mercury analysis has recently been used as an alternative to harvesting fish for fillets; however, there is limited information comparing fillet plug results to whole fillet results. This study was conducted to address that data gap and to test the applicability of plugs for monitoring associated with United States Environmental Protection Agency’s fish tissue-based mercury and selenium water quality criteria. The mercury phase included 300 fillet homogenates and 300 field-extracted plug samples from 60 fish, and the selenium phase included 120 fillet homogenates and 120 plugs from 30 fish. Both phases showed that there were no statistically significant differences between fillet plug and homogenized fillet results at the community level; however, a selenium plug monitoring alternative must employ a sufficiently sensitive analytical method and consider total solids. Plug and fillet sampling alternatives have inherent advantages and disadvantages. Fillet sampling provides sufficient mass to consider multiple contaminants but requires fish to be harvested. Plug sampling only provides adequate mass for a single analyte but may allow fish survival, although additional research is needed on survival following plug removal.

Using accepted methods, the physicochemical characteristics and microalgae composition of the water and sediment of Otamiri river were assessed. The results showed that the electrical conductivity (EC), turbidity, and biological oxygen demand (BOD) levels were higher than those allowed by the World Health Organisation (WHO). As expected, the dissolved oxygen (DO) level of 8.33mgL -1 was below the WHO standard of 10mgL -1 . Out of all the heavy metals discovered in the river water, iron had the highest quantity (0.542mgL -1 ). Similarly, concentrations of arsenic, mercury, and lead were found to exceed the WHO drinking water quality criteria. Nevertheless, there was no nickel, copper, or cadmium in the river water. The lowest and greatest quantities of arsenic (0.004 mg kg -1 ) and iron (1.789 mg kg -1 ) were found in the sediment, respectively. Benzethonium chloride was the most prevalent cationic surfactant in both the river water (3.9634mgL - 1 ) and the sediment (1.5631mgkg -1 ). Diethyl heptadecyl imidazolinium chloride and benzalkonium chloride exhibited the lowest concentrations in water and sediment, measuring 0.5408mgL -1 and 0.9758mgkg -1 , respectively. The amounts of cationic surfactants detected in the river water were all higher than the permissible limit of 0.5mgL -1 established by the Environmental Protection Agency (EPA) in 1979. The most concentrated anionic surfactant in sediment (5.6551mgkg -1 ) and water (2.0938mgL -1 ) was discovered to be sodium decylsulfate. Sodium tetradecylsulfate had the lowest amount in the water (0.0521mgL -1 ), however sodium octadecylsulfate was absent from the sediment. Both sodium decylsulfate and sodium octadecylsulfate levels were higher than those advised by the EPA. The concentrations of certain physicochemical parameters in soil samples and river water point to possible human-caused pollution of the aquatic environment. Aquatic creature disturbance, alterations in water chemistry, and bioaccumulation in the food chain are just a few of the ecological effects that these contaminants may have. The microalgae isolates were identified as Micractinium pusillum , Chlorella sorokiniana , and Dictyosphaeriun ehrenbagianum by BLASTn's partial 18S rRNA gene sequence similarity analysis.

Fish Bioaccumulation Factors (BAFs; ratios of mercury (Hg) in fish (Hgfish) and water (Hgwater)) are used to develop total maximum daily load and water quality criteria for Hg-impaired waters. Both applications require representative Hgfish estimates and, thus, are sensitive to sampling and data-treatment methods. Data collected by fixed protocol from 11 streams in 5 states distributed across the US were used to assess the effects of Hgfish normalization/standardization methods and fish-sample numbers on BAF estimates. Fish length, followed by weight, was most correlated to adult top-predator Hgfish. Site-specific BAFs based on length-normalized and standardized Hgfish estimates demonstrated up to 50% less variability than those based on non-normalized Hgfish. Permutation analysis indicated that length-normalized and standardized Hgfish estimates based on at least 8 trout or 5 bass resulted in mean Hgfish coefficients of variation less than 20%. These results are intended to support regulatory mercury monitoring and load-reduction program improvements.

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This paper reports on an investigation into determining nanogram/l quantities of mercury in marine and fresh water matrices using a cold vapour generation of mercury, followed by fluorescence detection. Samples were prepared for analysis using a free bromine oxidation technique. A high efficiency gas-liquid separator was used to enhance the detection of mercury. For fresh water, typical method detection limits (MDL) were determined at less than 1 nanogram/l (ng/l). For near shore seawater, the MDL was 1.2 ng/l. Method spikes, which were performed at 20 ng/l, showed mean recoveries within US EPA Contract Laboratory Protocol (CLP) acceptance criteria. System blanks averaged 0.12 ng/l, and recoveries of NIST 1641c diluted to 29.4 ng/l averaged 93.4%. A number of local rivers and streams were sampled, and mercury was determined. All results to date indicate mercury levels below the US EPA chronic water quality criteria for mercury.

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Suspended particulate matter (SPM) carries a major fraction of metals in turbid coastal waters, markedly influencing metal bioaccumulation and posing risks to marine life. However, its effects are often overlooked in current water quality criteria for metals, primarily due to challenges in quantifying SPM's contribution. This contribution depends on the SPM concentration, metal distribution coefficients (Kd), and the bioavailability of SPM-bound metals (assimilation efficiency, AE), which can collectively be integrated as a modifying factor (MF). Accordingly, we developed a new stable isotope method to measure metal AE by individual organisms from SPM, employing the widely distributed filter-feeding clam Ruditapes philippinarum as a representative species. Assessing SPM from 23 coastal sites in China, we found average AEs of 42% for Zn, 26% for Cd, 20% for Cu, 8% for Ni, and 6% for Pb. Moreover, using stable isotope methods, we determined metal Kd of SPM from these sites, which can be well predicted by the total organic carbon and iron content (R2 = 0.977). We calculated MFs using a Monte Carlo method. The calculated MFs are in the range 9.9-43 for Pb, 8.5-37 for Zn, 2.9-9.7 for Cu, 1.4-2.7 for Ni, and 1.1-1.6 for Cd, suggesting that dissolved-metal-based criteria values should be divided by MFs to provide adequate protection to aquatic life. This study provides foundational guidelines to refine water quality criteria in turbid waters and protect coastal ecosystems.

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Artisanal and small-scale gold mining, “Galamsey” as it is called in Ghana, within the Ankobra estuary has impacted the water quality, fish health and other aquatic organisms. This paper presents a study investigating the concentrations of mercury and lead in water, sediments, gills and liver of Chrysichthys nigrodigitatus of the Ankobra estuary. Bimonthly sampling between December 2020 and June 2021 was conducted at nine locations along the estuary. Physicochemical parameters such as temperature, dissolved oxygen, pH and turbidity were determined in situ using the EUTECH Multi-Parameter probe. A total of 36 water samples, 36 sediment samples and 120 fish samples were collected. Mercury (Hg) and lead (Pb) concentrations in the samples were measured using Atomic Absorption Spectrophotometry (AAS), employing appropriate techniques for each metal. Results showed that the physicochemical parameters of water, except for turbidity, were within the acceptable limits for aquatic life, based on the United States Environmental Protection Agency water quality criteria. Mercury and lead concentrations in water and fish samples exceeded United States Environmental Protection Agency guideline thresholds. In sediments, mercury levels surpassed both average shale values and ecological risk thresholds (ERM = 0.71 mg/kg), indicating high ecological risk, while lead remained below the ERL (46.7 mg/kg), suggesting low risk. Mercury and lead concentration in fish, water and sediments differ significantly (P < 0.05) across locations and between matrices (water, sediment, and fish organs). High bioaccumulation factors (BAFs) were recorded for both metals in fish. The BAF of mercury in fish-to-water samples was greater than in fish-to-sediment samples. In contrast, the bioaccumulation factor of lead was greater than in sediments compared to water. The study revealed that Ankobra estuary is polluted with mercury and lead and all necessary regulations should be enforced on the activities of artisanal miners to curb this menace.

Anthropogenic activities lead to environmental contamination with foreign substances such as heavy metals. This work was aimed to monitor trace elements (total arsenic (As), cadmium (Cd), chrome (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), and zinc (Zn)) contamination levels (dry weight base) in three natural freshwater reservoirs of Oman including Al Khawd and Al Amarat (Muscat Governorate) and Surur area (Ad Dakhiliyah Governorate as control area) using a native benthic inland fish (Garra shamal; Cyprinidae) for the first time. The muscle and liver of a hundred and twenty G. shamal were collected to assess the degree of metal contamination. Atomic absorption spectrometry was used as an analytical technique. From the spectrum of analyzed elements, we found Zn as a major element in monitored areas. The statistically significant (P < 0.05) highest concentrations of Zn liver (0.275 ± 0.065 µg/g) were in Al Amarat compared to the other areas. The concentrations of monitored elements in the fish muscle were lower than the liver samples. Furthermore, the fish length was significantly correlated with the accumulation of Hg and Co in both muscle and liver samples. In all analyzed fish from Oman inland water, the concentrations of elements were below the permissible limits; however, additional research is needed.

The present study investigates the bioaccumulation of heavy metals and associated histopathological alterations in Clarias batrachus (walking catfish) from selected aquatic ecosystems in Durg District, Chhattisgarh. This region, characterized by increasing industrial and agricultural activities, presents potential sources of metal contamination in freshwater bodies. Water, sediment, and fish samples were collected from three sites (high, moderate, and low contamination zones) and analyzed for cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr), and zinc (Zn) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Tissues (gills, liver, kidney, and muscle) of fish were examined for bioaccumulated metals and subjected to histopathological analysis. Results indicated significant bioaccumulation, particularly in metabolically active tissues such as the liver and kidneys. Correlation analysis revealed strong positive relationships between metal concentrations and lesion severity, with Hg and Cd showing the highest correlation in liver and gill tissues, respectively. Histopathological findings included epithelial lifting, lamellar necrosis, hepatocyte vacuolation, and tubular degeneration. Principal Component Analysis (PCA) highlighted the clustering of specific metals with organ-specific damage, while ANOVA confirmed significant differences in lesion severity across sites. This study affirms Clarias batrachus as an effective bioindicator and highlights histopathological biomarkers as sensitive tools for early detection of aquatic toxicity. The findings underscore the ecological risk posed by heavy metal pollution and stress the need for regulatory intervention, routine monitoring, and ecotoxicological assessments to safeguard both aquatic biodiversity and public health in Chhattisgarh and similar regions.

The Sea of Azov, an inland shelf sea bounding Ukraine and Russia, experiences the effects of ongoing and legacy pollution. One of the main contaminants of concern is the heavy metal mercury (Hg), which is emitted from the regional coal industry, former Hg refineries, and the historic use of mercury-containing pesticides. The aquatic biome acts both as a major sink and source in this cycle, thus meriting an examination of its environmental fate. This study collated existing Hg data for the SoA and the adjacent region to estimate current Hg influxes and cycling in the ecosystem. The mercury-specific model “Hg Environmental Ratios Multimedia Ecosystem Sources” (HERMES), originally developed for Canadian freshwater lakes, was used to estimate anthropogenic emissions to the sea and regional atmospheric Hg concentrations. The computed water and sediment concentrations (6.8 ng/L and 55.7 ng/g dw, respectively) approximate the reported literature values. The ongoing military conflict will increase environmental pollution in the region, thus further intensifying the existing (legacy) anthropogenic pressures. The results of this study provide a first insight into the environmental Hg cycle of the Sea of Azov ecosystem and underline the need for further emission control and remediation efforts to safeguard environmental quality.

The Tablas de Daimiel National Park (TDNP) is a floodplain ecosystem in central Spain with a potential risk of heavy metal and metalloid pollution. The objective of this study was to know the accumulation of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), and selenium (Se) in muscle of six species of freshwater fish from the floodplain of TDNP. We obtained muscle samples of Cyprinus carpio (n = 89); Squalius pyrenaicus (n = 16); Ameiurus melas (n = 9); Lepomis gibbosus (n = 8); Micropterus salmoides (n = 6) and Carassius auratus (n = 5). A. melas, which is a predatory species, had significantly higher Hg concentrations than omnivorous or herbivorous species (i.e. C. carpio). On the contrary, A. melas showed lower concentrations of As, Pb and Se than omnivorous species (i.e. S. pyrenaicus and L. gibbosus ). The concentration of Hg was positively associated with fish size in C. carpio and A. melas. Some individuals of C. carpio (5.7%) and S. pyrenaicus (12.5%) showed Pb muscle concentrations above the maximum residue levels established by the European legislation for human consumers. The observed muscle Se concentrations can be associated with adverse effects on fish such as blood changes, reduced growth, mortality of juveniles and reproductive failure. The accumulation of Se in this floodplain located in a seleniferous area and the contamination produced by spent Pb shot pellets used for hunting in the past are discussed as potential sources of the elevated levels of these two elements in fish from this floodplain wetland.

Rawa Taliwang is one of the major lakes in West Sumbawa Regency and is vulnerable to mercury (Hg) contamination resulting from surrounding activities such as illegal gold mining, agricultural runoff, and domestic waste disposal. This study aimed to determine the mercury concentration in catfish (Clarias batrachus) inhabiting the lake and to assess its safety for human consumption. Fish samples were collected from two sampling stations using purposive sampling and analyzed in the laboratory using a Mercury Analyzer. The measured mercury concentrations ranged from 0.058 to 0.086 mg/kg, with an average of 0.072 mg/kg, which is below the maximum allowable limit of 0.50 mg/kg set by the Indonesian National Agency for Drug and Food Control (BPOM) Regulation No. 9/2022. These results indicate that catfish from Rawa Taliwang Lake remain safe for consumption. Continued monitoring and improved environmental management are recommended to prevent future increases in mercury contamination and to ensure long-term ecosystem and public health safety.

Environmental pollution is a worldwide problem; heavy metals constitute one of the most important pollutant challenges. The progress of industry has led to increased emission of pollutants into ecosystem. Environmental pollution can cause poisoning, diseases and even death to fish. Heavy metal contamination has gradually become a very much important significant global issue due to its continual existence in the environment and bioaccumulation in the ecosystems, posing deleterious risks to human health. Mercury contamination is amongst the most significant and universal pollution problems in the aquatic medium It primarily occurs in the aquatic environment In industries, huge amounts of effluents containing mercury are discharged as a result of poor industrial operations, fertilizer industry, landfill leaching, and carbon combustion. Dead zones, otherwise termed as zones of oxygen-depleted water, have been reported to be the repository of huge deposits of inorganic mercury. Fish are one of the most widely distributed organisms in the aquatic environment and, being susceptible to metal contamination, may reflect the extent of the biological effects of metal pollution in waters. The effect of mercury chloride on protein and amino acid contents of gill, liver and kidney of freshwater fish, Hypophthalmichthys molitrix have been studied. The fish were exposed to sublethal concentrations of mewrcury chloride 1/5th (high), 1/10th (medium) and 1/15th (low) of the 96 hour LC50 for the period of 10, 20 and 30 days. All the sublethal concentrations of mercury chloride exposed fish for the period of 10. 20 and 30 days showed decrease the protein and increase the amino acid content in gill, liver and kidney of Hypophthalmichthys molitrix The significant alterations showed toxic effect of heavy metal mercury chloride at biochemical levels.

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The present study investigates the distribution of cadmium, chromium, and mercury levels in sediments, plants, and fish from Zemplínska Šírava, a historically contaminated reservoir in Slovakia. Using fish as bioindicators, we analyzed the impact of factors such as age, gender, ecological group, and parasite burden on heavy metal accumulation. Results revealed that mercury was highest in fish muscle, particularly predatory species, whereas chromium and cadmium were predominantly found in liver tissues. Chromium accumulation was influenced by gender, with females showing higher levels. Older fish exhibit greater cadmium accumulation in liver tissue. Parasite burden was associated with elevated mercury levels in fish muscle. Notably, the cestode Caryophyllaeus laticeps had significantly higher chromium levels than its host, freshwater bream (Abramis brama). This study highlights the important role of fish and parasites in monitoring aquatic contamination and illustrates the complex interplay of biological and environmental factors in heavy metal bioaccumulation.

We analyzed whole genome sequences of 308 Escherichia coli isolates from a marine ecosystem to determine the prevalence and relationships of heavy metal resistance genes (HMRGs) and antibiotic resistance genes (ARGs), as well as the presence of plasmid sequences. We screened all genomes for presence of 18 functional HMRGs conferring resistance to arsenic, cadmium, copper, or cadmium/mercury. In subset analyses, we examined geographic variations of HMRG carriage patterns in 224 isolates from water sources, and sought genetic linkages between HMRGs and ARGs in 25 genomes of isolates resistant to antibiotics. We found high carriage rates of HMRGs in all genomes, with 100% carrying at least one copy of 11 out of 18 HMRGs. A total of 173 (56%) of the isolates carried both HMRGs and plasmid sequences. In the 25 genomes of antibiotic-resistant isolates, 80% (n = 20) carried HMRGs, ARGs, and plasmid sequences, while 40% (n = 10) had linked HMRGs and ARGs on their assembled genomes. We found no evidence of geographic variation in HMRG frequency, nor any association between locational proximity to Superfund sites and co-carriage of HMRGs and ARGs. Our study findings indicate that HMRGs are common among E. coli in marine ecosystems, suggesting widespread heavy metal presence in water sources of a region with history of environmental pollution. Further research is needed to determine the role HMRGs play in driving antimicrobial resistance in human pathogens through genetic linkage and the value their detection in environmental bacterial genomes may offer as an indicator of environmental heavy metal pollution.

The present study assessed Cybister lateralimarginalis as a model species for ecotoxicological studies of metal(loid) bioaccumulation in freshwater ecosystems, by optimising protocols and analysing biomarker activities and metal(loid) concentrations from different sites and investigating their association. To accomplish this, levels of arsenic (As), selenium (Se), cadmium (Cd), mercury (Hg), and lead (Pb) were analysed, as well as a set of biomarkers were evaluated, esterase activity and oxidative stress biomarkers: fluorescence- and glutathione-based. C. lateralimarginalis were sampled in the spring/summer of 2023 along the Sava, Drava and Danube floodplains in Croatia. C. lateralimarginalis samples from Sava floodplain (Mužilovčica) showed altered carboxylesterase (CES) activity, lower glutathione (GSH) levels, and elevated Hg and As concentrations. The Weighted Pollution Index (WPI) indicated moderate pollution at the Sava floodplain, possibly due to agricultural or petrochemical impacts. At the Drava floodplain (Podravlje), higher glutathione S-transferase (GST) activity and elevated Cd, Hg, and As concentrations were observed, likely from soil accumulation, while Stara Drava beetles had lower GSH levels, suggesting agricultural impacts. Despite this, the Drava floodplain showed the lowest WPI. Higher GST activity was noted at the Danube floodplain (Kopački rit and Topoljski Dunavac), with reactive oxygen species (ROS) concentrations (Kopački rit and Podunavlje) possibly reflecting agricultural practices or illegal hunting. The present research successfully applied C. lateralimarginalis as a bioindicator species for assessing metal(loid)s in different environments, highlighting its reliability as an abundant apex predator, emphasizing the significance of integrating biomarker response evaluation into pollutant monitoring for efficient environmental risk assessment in freshwater ecosystems.

Heavy metal bioaccumulation in aquatic organisms of open water aquatic ecosystems was detected globally, including Bangladesh. This study evaluated the hypothesis of whether heavy metal contamination in aquatic habitats impacts fish growth and reproduction using wild Channa punctata as an experimental animal. The growth and reproductive health of a wild freshwater fish, C. punctata, collected from five freshwater habitats, were assayed with heavy metal bioaccumulation. Atomic absorption spectrometry detected the bioaccumulation of cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb) in the muscle of C. punctata. Cd, Cr, and Pb concentrations were the highest in the specimen collected from the Turag River and the lowest in the Dharla River. The highest concentration of Hg was found in C. punctata specimens collected from the Karatoya River (0.093 ± 0.004 mg/kg). The length-weight relationship and condition factor of C. punctata indicated a negative allometric growth pattern (b < 3.0) and poor wellness (F < 1.0) in all the stocks except Dharla River. We estimated the size at first sexual maturity (L50), ova diameter, fecundity, and gonadosomatic index (GSI) to assess reproductive health and determined the correlation with heavy metal bioaccumulation. We found that higher bioaccumulation of heavy metal impairs the reproductive health of C. punctata by lowering spawning performance. This study showed that heavy metal bioaccumulation impaired fish's growth and reproductive health, potentially affecting future recruitment and fishery sustainability.

Gold mining in Aceh Jaya, specifically in Gunong Ujeun, results in the discharge of waste water containing heavy metals into nearby rivers. This can negatively impact the environment, particularly through contamination by lead and mercury. These heavy metals can be toxic to aquatic life, potentially disrupting the food chain. Kijing clams, a type of shellfish commonly found in freshwater rivers, are particularly susceptible to metal accumulation due to their filter feeding behavior. This research aims to assess the impact of lead and mercury levels in the Krueng Sabe river on the accumulation of these metals in shellfish, exceeding the threshold set for the river in Aceh Jaya Regency. The study will use Atomic Absorption spectroscopy (AAS) to measure the heavy metal content. The results show that the lead content in shellfish meat is 0.191 mg/kg, while the mercury content is 0.255 mg/kg. These levels are below the maximum limits set for heavy metals in food.

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Heavy metals, due to their toxicity, persistence, and non-biodegradability, have become some of the most severe environmental pollutants globally. Their accumulation in lake sediments can significantly impact aquatic ecosystems' biogeochemical cycles by altering the ecological dynamics of microbial communities. To further elucidate the mechanisms underlying microbial responses to complex heavy metal pollution in lake sediments, sediment samples were collected from Nan Yi Lake, and their physicochemical properties and microbial composition were systematically analyzed. The results demonstrated that the sediments of Nan Yi Lake were significantly contaminated with heavy metals, which were identified as the predominant factors shaping microbial community structure. Heavy metals influenced microbial richness and distribution patterns along sediment depth gradients, driving the establishment of optimal ecological niches. Meanwhile, other physicochemical factors indirectly affected microbial communities by modulating the concentration of heavy metals. Furthermore, the microbial co-occurrence network was closely associated with the concentrations of Fe and As, with sediment particle size also playing a contributing role. This study highlights the intricate interactions between physicochemical factors and microorganisms, offering critical insights into the multifaceted impacts of heavy metal compound pollution on lake ecosystems. It provides a scientific foundation for effective management of lake environmental pollution and ecological restoration efforts.

Heavy metal (HM) pollution is a major concern in freshwater ecosystem management. The different types of endogenous organic matter and the way their decomposition affects HM transformation in freshwater lakes is not well understood. An ex situ mesocosm study was conducted to compare HM transformation in sediments during anaerobic decomposition of cyanobacterial bloom biomass (CBB) and submerged cyanobacterial vegetation in Lake Taihu, known as Potamogeton malaianus (PM). Microbial community structures were examined through Illumina sequencing of 16S rDNA. Results indicate that Zn had a remarkably higher amount of potential mobile fraction than other heavy metals (Cr, Pb, Cu, Ni, and Cd) detected in sediments, especially in sediments collected from CBB-dominated areas (approximately 150 mg kg-1). CBB decomposition has caused a significant increase in exchangeable Zn content in sediments and a decrease in reducible Zn that was three times greater than PM decomposition. Additionally, oxidizable Zn content declined during CBB decomposition but increased during PM decomposition. Furthermore, the relative abundance of the main fermentative bacteria and some sulfate-reducing bacteria genera (e.g., Desulfomicrobium) were significantly associated with the HM content of exchangeable and reducible fractions during CBB decomposition. Overall, the findings indicate that Zn is more susceptible to endogenous organic matter decomposition than other metals in freshwater lakes, and the impacts of CBB decomposition on the transformation of heavy metals in sediment are greater than that of submerged macrophyte decomposition.

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Heavy metal contamination in freshwater ecosystems has emerged as one of the most pressing ecotoxicological challenges of the twenty-first century, particularly in rapidly industrialising regions of South Asia. This study investigated the histopathological and physiological responses of the freshwater teleost Labeo rohita (Hamilton, 1822) following sub-lethal exposure to a multi-metal mixture (Pb, Cd, Cr, Cu, Zn, Hg, As, and Ni) sourced from industrial effluents discharged into the Krishna River basin, Telangana. The 96-hour LC50 concentrations were administered to fish at 10, 25, and 50 percent concentration after 28 days under a controlled laboratory environment. Hematologic tests showed a progressive decrease in red blood cell count, haemoglobin, and haematocrit dose-dependently with significant leucocytosis, which was a sign of immunosuppression and oxidative stress. Marked increases in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), glucose, and cortisol levels affirmed the presence of hepatotoxicity and systemic stress responses. A histopathology of liver, gill, kidney, and spleen revealed progressive lesions such as hepatocyte swelling, lamellar fusion, glomerular atrophy, and lymphocyte depletion. Higher doses of antioxidant enzymes, superoxide dismutase and catalase, were rather inhibited, but malondialdehyde levels increased, and this proved that lipid peroxidation has taken place. The results clearly prove that sub-lethal exposure to heavy metals induces extreme and multi-organ toxicity in freshwater fish with dire consequences on aquatic biodiversity and human health in industrial areas of Telangana.

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Heavy metal contamination in freshwater systems poses critical risks to aquatic organisms, particularly through bioaccumulation and sublethal cellular damage. This study evaluates the use of genotoxic and histopathological biomarkers – specifically micronucleus (MN) formation in erythrocytes and gill tissue alterations – in wild cyprinidae as indicators of heavy metal pollution along the Brantas River, Malang, Indonesia. Fish were sampled from three sites representing an upstream-to-downstream gradient: Batu (Site A), Dinoyo (Site B), and Kepanjen (Site C). Gill tissues from 180 individuals were analyzed for lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), and zinc (Zn) concentrations using atomic absorption spectrophotometry. Genotoxicity was assessed through MN assays on peripheral blood erythrocytes, while gill histopathological changes were evaluated and quantified using a gill histo - pathological index (GHI). Results demonstrated a clear spatial increase in metal accumulation, with Pb levels rising from 0.85 ± 0.22 mg/kg at Site A to 4.87 ± 0.61 mg/kg at Site C. Correspondingly, MN frequency increased from 1.34 ± 0.41‰ to 6.92 ± 0.88‰, and GHI scores rose from 3.2 ± 0.9 to 11.4 ± 2.2. The increases in micronucleus frequency (p < 0.001), gill histopathology scores (p < 0.001), and heavy metal concentrations (p < 0.01 to p < 0.001) across sites were statistically significant, confirming a strong correlation between pollution level and biological responses. Significant correlations were observed between heavy metal concentrations and both MN frequency and gill pathology severity. These findings validate the combined use of MN assay and gill histopathology as sensitive, complementary biomarkers for monitoring heavy metal pollution in riverine ecosystems. The study underscores the need for integrated biomonitoring strategies and strengthened pollution management in tropical freshwater systems

Heavy metals (HMs) in suspended particulate matter (SPM) present critical ecological and health concerns due to their mobility, bioavailability, and toxicity in aquatic systems. However, the speciation and associated ecological risks of HMs in freshwater SPM remain inadequately characterized. This study investigated the concentrations, speciation, and ecological risks of ten HMs (Cr, Ni, Cu, Zn, As, Cd, Pb, Mn, V, and Co) in paired SPM-sediment matrices across five representative small and medium-sized lacustrine and fluvial ecosystems in Southwest China, using a modified European Community Bureau of Reference (BCR) sequential extraction method combined with multiple risk assessment approaches. Results showed that Mn exhibited the highest enrichment in SPM, with concentrations 8.8-fold higher in lake systems and 2.6-fold higher in river systems compared to sediments. BCR analysis further revealed that, compared to sediments, SPM had a higher proportion of reducible fractions, implying the presence of substantial amounts of recently formed, authigenic Mn oxides in SPM. Geoaccumulation index (Igeo) indicated that Cd, Mn, and Zn were the predominant contaminants in SPM across all systems. These three metals exhibited the highest proportions in the exchangeable fraction, and SPM contained greater exchangeable fractions than sediments, suggesting enhanced mobility and bioavailability. Multidimensional risk assessment demonstrated that SPM-associated metals, especially Mn, posed greater ecological and health risks (particularly for children) than those in sediments. Overall, this study highlights SPM as both a carrier and a secondary source of HMs in freshwater systems, underscoring the need for targeted monitoring and management strategies to reduce labile HM inputs and protect aquatic ecosystem health.

Freshwater bodies are a vital resource for humans, yet they are threatened by numerous factors, many of which remain unidentified. In this study, we assessed the concentrations of seven heavy metals (HMs) in forty-eight water samples and analyzed their correlation with zooplankton populations and human health risks at four sub-divisional sites in West Bengal, India. Sampling was conducted throughout the year. We used indices based on HMs and zooplankton to evaluate human health risks. The results revealed that the total taxonomic richness of zooplankton (Rotifera, Copepoda, and Branchiopods) was 72 species, with Rotifera richness 25, Copepoda 37, and Branchiopods 10 species. These results demonstrated a negative correlation between zooplankton abundance and HMs concentration, highlighting zooplankton’s potential as significant indicator species. Pearson’s correlation analysis revealed a significant relationship between HMs concentration and zooplankton abundance (P < 0.05). Among the four sub-divisional areas studied, Haldia exhibited the highest level of heavy metal pollution, with 40.47% of heavy metals posing potential health risks (HQ > 1) to both adults and children due to industrial effluent compared to the other study sites. Overall, the Metal Index and Nemerow Pollution Index indicated that 83.34% and 97.92% of water samples, respectively, were contaminated by heavy metals. Among the heavy metals, Nickel (Ni) and Zinc (Zn) were identified as having the highest health risk potential for both groups. The Health Hazard Index (HI) values suggested that children are at higher risk (HI > 1) compared to adults. Specifically, the HQ-ingestion rate was higher in children, while the HQ-dermal (HQd) contamination was higher in adults. Throughout the assessment period, both children and adults were found to be at potential health risk from heavy metals. These findings provide baseline information crucial for addressing environmental health risks and promoting sustainable practices.

Municipal landfill leachates are a source of toxic heavy metals that have been shown to have a detrimental effect on human health and the environment. This study aimed to assess heavy metal contamination in leachates, surface water, and sediments from non-sanitary landfills in Uyo, Nigeria, and to identify potential health and environmental effects of leachate contamination. Over the wet and dry seasons, surface water and sediment samples were collected from an impacted freshwater ecosystem, and leachates samples from six monitoring wells. Elemental analyses of samples were conducted following standard analytical procedures and methods. The results indicated that leachate, surface water, and sediment samples all had elevated levels of heavy metals, implying a significant impact from landfills. Pollution indices such as the potential ecological risk index (PERI), pollution load index (PLI), degree of contamination (Cd), modified degree of contamination (mCd), enrichment factor (EF), geoaccumulation index (Igeo), and Nemerov pollution index (NPI) were used to assess the ecological impacts of landfill leachates. The following values were derived: PERI (29.09), PLI (1.96E-07), Cd (0.13), mCd (0.16), EF (0.97–1.79E-03), Igeo (0), and NPI (0.74). Pollution indicators suggested that the sediment samples were low to moderately polluted by chemical contaminants from the non-sanitary landfills, and may pose negative risks due to bioaccumulation. Human health risks were also assessed using standard risk models. For adults, children, and kids, the incremental lifetime cancer rate (ILCR) values were within the acceptable range of 1.00E-06–1.00E-04. The lifetime carcinogenicity risks associated with oral ingestion exposure to heavy metals were 9.09E-05, 1.21E-05, and 3.60 E-05 for kids, adults, and children, respectively. The mean cumulative risk values for dermal exposures were 3.24E-07, 1.89E-06, and 1.17E-05 for adults, children, and kids, respectively. These findings emphasized the risks of human and biota exposure to contaminants from landfills.

No abstract available

A seasonal characterization of mercury (Hg) accumulation in three different estuaries along the Portuguese coast (i.e. Ria de Aveiro, Tagus estuary and Ria Formosa) was done. For that, it was evaluated: (1) Hg concentrations in abiotic (water) and biotic matrices (flora and fauna); (2) the risk of consumption of local seafood species (e.g. bivalves) to human health; and (3) the environmental risk to Hg exposure. During 1 year, water and biological samples were collected during low tide, in each system for Hg quantification. Our findings revealed that total Hg concentrations in surface waters were higher in Ria de Aveiro and Tagus estuary than in Ria Formosa. In Ria de Aveiro, a particular attention should be given in autumn periods, where Hg levels (≈ 100 µg L^−1) were considered quite high according to European quality parameters. The same was observed for the Tagus estuary during spring time. Regarding macrofauna Hg levels, no clear seasonal trend was observed. Also, total Hg concentrations in edible species (< 0.5 µg. g^−1 ww) represent no risk for consumption. However, considering the environmental risk, in Ria de Aveiro, there is a moderate risk (RQ > 0.1) in autumn periods, which can be a matter of concern.

Mercury (Hg) is a heavy metal of global concern because of its persistence in the environment and its ability to bioaccumulate and biomagnify in ecosystems. Despite evidence of extensive environmental pollution in the Copperbelt Province, few studies have investigated Hg contamination in the Kafue River and its tributaries in Kitwe District, Zambia. Total Hg concentrations were determined in soil, sediments, and tilapia by inductively coupled plasma mass spectrometer (ICP-MS) from the mining areas and non-mining areas. There were significant differences in the population means for soil samples (Mean (mining) = 1.066, Mean (non-mining) = 0.041, p≤0.05\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le 0.05$$\end{document}) and sediment samples (Mean (mining) = 1.304, Mean (non-mining) = 0.034), p≤0.05\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le 0.05$$\end{document}) between mining and non-mining areas. There were also statistically significant differences in the population means for fish samples (Mean (mining) = 0.015, Mean (non-mining) = 0.007, p≤0.05\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le 0.05$$\end{document}) between mining and non-mining areas. The levels of Hg in the soil and sediments from the mining area were higher than the United States Environmental Protection Agency (USEPA) reference values of 0.3 mg/kg and 0.2 mg/kg, respectively. There was a weak positive correlation between the size of the fish (length) and Hg accumulation in the Kitwe mining area (r = 0.232, P = 0.1166). The observed correlation between Hg accumulation and length of fish was not statistically significant (P > 0.05). The EDI from the consumption of fish from the mining area was below the USEPA and WHO/FAO maximum tolerable daily intake of 0.1 µg/kg/day and 0.23 µg/kg, respectively. The THQ < 1 was also reported in the current study, suggesting that the exposure level may not cause adverse health effects during a lifetime in the human population. Although the EDI and THQ < 1 in the current study were below the USEPA and WHO/FAO maximum tolerable limit, the presence of Hg in fish in this area must be monitored due to its ability to bioaccumulate in large and predatory fish. The lower EDI value reported in the current study might be attributed to the smaller size of the tilapia fish specimens, resulting in low bioaccumulation of Hg. Since the Hg levels in sediments were above the USEPA limit, we recommend further studies on the bioavailability of Hg in humans and other fish species in the region, particularly carnivorous fish, due to Hg biomagnification to offer a clearer perspective on the environmental and health impacts.

Mercury contamination from gold mining in the Amazon poses significant environmental and health threats to the biome and its local populations. The recent expansion of non-industrial mining areas has severely impacted territories occupied by traditional communities. To address the lack of sampling data in the region and better understand mercury dynamics, this study used the probabilistic model SERAFM to estimate the mercury distribution and bioaccumulation in fish. The analysis covered 8,259 sub-basins across three major Amazonian basins: the Branco, Tapajós and Xingu rivers. The findings revealed increasing downstream mercury levels, with notable accumulations in the main watercourses influenced by methylation processes and mining releases. The projected concentrations showed that an average of 27.47% of the sub-basins might not comply with Brazilian regulations, rising to 52.38% in the Branco and Tapajós river basins separately. The risk assessment of fish consumption based on the projections highlighted high mercury exposure levels among traditional communities, particularly indigenous populations, with an average of 49.79% facing an extremely high risk in the Branco and Tapajós river basins. This study demonstrated SERAFM’s capacity to fill information gaps in the Amazon while underscoring the need for enhanced data collection, culturally sensitive interventions and regulatory updates to mitigate mercury contamination in gold mining-affected areas.

Heavy metal and microplastic pollution are a threat to marine ecosystems. Thus, the present study aims to assess the risk of these contaminants on edible organisms. Water and tissues of macroalgae, prawns, and crabs collected from 27 sites (3 zones) across the Gujarat coast were evaluated for heavy metal and microplastic presence. Chromium and nickel concentrations were highest in water samples of Alang and Nishkalank and in muscles of Penaeus japonicus, and Portunus sanguinolentus, while copper was highest in Ulva lactuca. Additionally, the bioconcentration factor highlighted mercury accumulation in macroalgae and nickel in prawns and crabs. Water and tissue samples revealed an abundance of microplastics (0.5- 4 mm) consisting of threads (49 %), fragments (33 %), and films (18 %) representing polymers like polyvinyl chloride, nylon, polypropylene, and polystyrene. Our findings indicate that contamination exceeds permissible limits in all three trophic levels studied, attributed to elevated anthropogenic activities, requiring immediate intervention for policy-driven decisions.

Mercury and arsenic are two highly toxic pollutants, and many researchers have explored the effects of the two substances on the environment. However, the research content of toxic substances in frozen periods is relatively small. To explore the spatial and vertical distribution of mercury and arsenic in the ice, water, and sediments of Wuliangsuhai Lake under ice conditions, and to assess the harm degree of the two toxic substances to human beings. We collected the ice, water, and sediments of the lake in December 2020, and tested the contents of Hg and As. The single-factor pollution index method, the local cumulative index method, and the ecological risk coding method were used to assess the pollution status in these three environmental media, and the Monte Carlo simulation combined with the quantitative model recommended by USEPA was used to assess the population health risk. The results showed that (1) The average single-factor pollution values of Hg and As in water were 0.367 and 0.114, both pollutants were at clean levels during the frozen period. (2) The mean Igeo values of Hg and As were 0.657 and −0.948. The bioavailability of Hg in the sediments of Wuliangsuhai Lake during the frozen period was high, and its average value was 7.8%, which belonged to the low-risk grade. The bioavailability of As ranged from 0.2% to 3.7%, with an average value of 1.3%. (3) Monte Carlo simulation results indicate acceptable levels of health risks in both water and ice. This study preliminarily investigated the distribution characteristics of toxic substances and their potential effects on human health in lakes in cold and arid regions during the frozen period. It not only clarified the pollution characteristics of lakes in cold and arid regions during the frozen period, but also provided beneficial supplements for the ecological protection of lake basins. This study lays a foundation for further environmental science research in the region in the future.

Mercury is an element with potential risk to fish and those who consume it. Thus, this study aimed to determine the levels of total mercury (THg), carry out a health risk assessment related to the consumption of the freshwater stingrays Potamotrygon motoro, and determine the physical and chemical properties of the water where stingrays occur. Stingrays of the species P. motoro were obtained from the Amazon River, and samples of the animals’ musculature were collected to determine THg levels. Risk assessment was conducted using pre-established formulas of estimated monthly intake (EMI), maximum monthly intake rate (IRmm), and hazard quotient (HQ). Three population scenarios were evaluated, considering both sexes and differences between rural and urban areas. There was no relationship between weight and THg concentration nor between total length and THg concentration. Higher EMI values were observed in rural children; for the IRmm, male children had the lowest consumption levels. For the hazard quotient, there was a similarity between the three age groups when comparing the male and female sexes. In addition, the representatives of the rural area always had lower values than the urban area. Freshwater stingrays, like other elasmobranchs, can be crucial animal species because they act as sentinels in studies that assess harmful chemicals like mercury.

Fish constitutes an essential source of high-quality protein and is, at the same time, the source of exposure to many hazardous contaminants, namely mercury and methyl mercury (MeHg). This study aims at assessing the risk that MeHg poses to the health of adult Qatari residents through fish consumption. Data on fish consumption were collected using a self-administered online survey composed of three sections that collected information about the fish-eating patterns of the participants. The fish species that were reported to be consumed by ≥ 3% of the respondents were sampled and analyzed for their total mercury (T-Hg) content levels. MeHg concentrations were derived from T-Hg content levels using a scenario-based approach. Disaggregated fish consumption and contamination data were combined using the deterministic approach to estimate MeHg intakes. The average, 75th, and 95th percentiles of the MeHg intake estimates were determined and compared to the tolerable weekly intake (TWI) set by the European Food Safety Agency (EFSA) (1.3 μg·kg^−1·w^−1). All fish samples contained T-Hg at levels ˂ 0.3–0.5 µg/g with a mean value of 0.077 µg/g. The study population had an average fish consumption of 736.0 g/week. The average estimated weekly intakes of MeHg exceeded TWI for some fish consumers including females of childbearing age and those following a high-protein diet. Our study highlights the need to establish regulatory guidelines and dietary advice based on risk/benefit ratio.

No abstract available

Mercury (Hg) is a widespread heavy metal causing various damages to health, while insufficient studies assessed its exposure risk across China. This study explored concentrations in food items and dietary exposure risks across China by comprehensively analyzing the researches on total Hg (THg) in eight food items and methylmercury (MeHg) in aquatic foods published between 1980 and 2021. According to the included 695 studies, the average THg concentration in all food items was 0.033 mg/kg (ranging from 0.004 to 0.185 mg/kg), with the highest concentration in edible fungi. The average daily dietary THg exposure from all foods was 12.9 μg/day. Plant-based foods accounted for 62.7% of the dietary THg exposure. Cereals and vegetables were the primary source of THg exposure. The MeHg concentration in aquatic foods was 0.08 mg/kg, and the average dietary exposure was 3.8 μg/day. Monte Carlo simulations of the dietary exposure risk assessment of THg and MeHg showed that approximately 6.4 and 7.0% of residents exceeded the health-based guidance value set by the European Food Safety Authority, with higher exposure risk in Southwest and South China. The nationwide target hazard quotient index of THg was greater than 1, suggesting that the non-carcinogenic risk of dietary exposure to THg needed further concern. In summary, this study has a comprehensive understanding of dietary Hg exposure risks across China, which provide a data basis for Hg exposure risk assessment and policy formulation.

The risk to human health from exposure to certain pollutants through the consumption of fruits, tubers, and fish were evaluated in a settlement located in a Colombian area highly impacted by gold mining activities. The concentrations of mercury (Hg) and arsenic (As) in edible food tissues and methylmercury (MeHg) in fish were determined for risk assessment. A questionnaire-based dietary survey was answered by 178 residents of three population groups: children (CHD), women of childbearing age (WCBA), and the rest of the population (RP). The estimated weekly intake (EWI) of MeHg presented values of 1.9 and 2.4 times higher than the provisional tolerable weekly intake (1.6 μg/kg BW/week) recommended by the FAO/WHO for CH and WCBA, respectively. The results of the HQ values of As and Hg for different food were above the safety level (HQ < 1) for most of the groups. For Hg, the highest HQ values correspond to fish, whereas for As in most of the food, but specially in fruits. The total target hazard quotients (HI) were higher than 1, in all the groups (except for CHD that consume tubers) indicating potential non-carcinogenic health risks. The values of carcinogenic risk (CR) for As through exposure to food ranged from 1.2 10-4 to 7.7 10-4, well above than the safety level of US EPA risk (10-4 - 10-6), suggesting the probability of carcinogenic risk for the entire population via ingestion. Therefore, safety control mechanisms and environmental education strategies should be applied to address food intake, associated with good agricultural practices to provide solutions to protect the health of the residents in areas affected by gold mining activities.

Environmental pollution is one of the major problems facing the human society today. Rapid industrialization coupled with urbanization has contaminated the aquatic ecosystems through heavy metals (Islam & Tanaka, 2004; Mwanamoki et al., 2015; Ali et al., 2019). Due to their persistence, heavy metals pose a serious risk on living organisms and the aquatic ecosystems (Ullah et al., 2017, Fuentes-Gandara et al., 2018; Ogbomida et al., 2018). In addition, their bioaccumulation and magnification through the water, sediments and food chain (Omar et al., 2013; Liu et al., 2018; Kumari &Maiti, 2020) have given heavy metals the potential to pose delitrious threat. Arsenic and mercury are contaminants of a particular concern attributed to their wide distribution in the environment and their high potential for bioaccumulation and biomagnification (Lavoie et al., 2013; Qiu et al., 2018; Marziali & Valsecchi, 2021). In freshwater systems, the accumulation of As and Hg has been detected in sediment originated from anthropogenic inputs; sediment can act as a potential secondary source of the contaminant for overlaying waters and aquatic organisms (Amos et al., 2014; Marziali & Valsecchi, 2021). According to public health guidelines, As and Hg are ARTICLE INFO ABSTRACT Article History: Received: June 12, 2023 Accepted: July 15, 2023 Online: Aug. 2, 2023 _______________

No abstract available

The present study aimed to assess corocoro grunt use as bioindicator of Hg contamination in coastal marine systems by testing environmental (seasons) and biological effects (sexual maturity, size and weight) on THg accumulation and assessing human health risk. Fish was captured in winter and summer seasons at Vermelha Beach, Rio de Janeiro, Southeast Brazil. Adult O. ruber showed significantly higher THg than juveniles, and THg concentrations were positively correlated to fish length and weight. Fish THg concentrations did not differ between seasons and were below the accepted limit for human consumption. Human exposure risk by fish consumption was 0.31 μg MeHg kg-1 week-1 and the hazard quotient was 0.44 (0.11-1.84). Our results confirm the applied use of O. ruber as sentinel species for Hg contamination monitoring and highlight concern for its consumption, especially for local fishermen populations that highly consume this fish and may be more susceptible to Hg adverse effects.

Mercury (Hg), lead (Pb), and cadmium (Cd), commonly termed "the toxic trio," are highly toxic metals regulated in food by the European Union for consumer safety. This study examined the biological and environmental factors influencing their accumulation in marine organisms by analyzing trace metal concentrations in the muscle tissue of 10 species with varied habitat preferences (seven teleosts, two elasmobranchs, and one crustacean) caught in the Northwestern Mediterranean. Shark samples across different size ranges were analyzed to identify accumulation patterns. Geographical variability was evaluated using the small-spotted catshark (Scyliorhinus canicula) as a biomonitor, comparing Mediterranean results with data from Atlantic Spanish regions and published values. Compliance with European regulations and associated consumer risks were also assessed. Hg accumulation showed interspecific variation linked to habitat use, with the highest levels in benthic species, and intraspecific accumulation positively correlated with size. Geographically, Hg levels were higher in the Northwestern Mediterranean, reflecting the region's high methylation potential. While Pb and Cd remained within European consumption limits, over one-third of benthic samples exceeded Hg thresholds, and 92.45% of adult sharks surpassed safe levels, compromising their commercialization. Mediterranean benthic fish should be consumed sparingly, particularly by pregnant women and children, as recommended for top predator species. This study highlights how habitat use and body size drive Hg accumulation, establishes S. canicula as a biomonitor for contamination, and underscores the role of regional environmental factors in shaping metal distribution and bioavailability, contributing to a better understanding of Hg fate in marine ecosystems and its potential impact.

Fish serves as the principal source of animal protein for the indigenous people of the Amazon, ensuring their food and nutritional security. However, gold mining causes mercury (Hg) contamination in fish, and consequently increases health risks associated with fish consumption. The aim of this study was to assess the health risk attributed to the consumption of mercury-contaminated fish by Munduruku indigenous communities in the Middle-Tapajós Region. Different fish species were collected in the Sawré Muybu Indigenous Land to determine mercury levels. The health risk assessment was carried out according to the World Health Organization (WHO 2008) methodology and different scenarios were built for counterfactual analysis. Eighty-eight fish specimens from 17 species and four trophic levels were analyzed. Estimates of Hg ingestion indicated that the methylmercury daily intake exceeds the U.S. EPA (United States Environmental Protection Agency) (2000) reference dose from 3 to 25-fold, and up to 11 times the FAO (Food and Agriculture Organization)/WHO (2003) dose recommendation. In all situations analyzed, the risk ratio estimates were above 1.0, meaning that the investigated Munduruku communities are at serious risk of harm as a result of ingestion of mercury-contaminated fish. These results indicate that, at present, fish consumption is not safe for this Munduruku population. This hazardous situation threatens the survival of this indigenous population, their food security, and their culture.

The development of both detection and removal technologies for heavy metal ions is of great importance. Most of the existing adsorbents that contain oxygen, nitrogen or sulfur functional groups can remove heavy metals, but achieving both selective detection and removal of a single metal ion is difficult because they bind to a wide range of heavy metal ions. Herein, we selected zeolite imidazolium hydrochloride framework-71 (ZIF-71) with sufficient chlorine functional groups to fabricate magnetic ZIF-71 multifunctional composites (M-ZIF-71). M-ZIF-71 had a large specific surface area, excellent water stability, and good magnetic properties, which made M-ZIF-71 conducive to the separation and recovery of adsorbents and the assembly of electrodes. M-ZIF-71 exhibited high selectivity, wide linear range (1-500 μg/L), and low detection limit (0.32 μg/L) for electrochemical detection of mercury ions (Hg2+). Meanwhile, M-ZIF-71 demonstrated rapid Hg2+ adsorption with a high capacity of 571.2 mg/g and excellent recyclability. The high selectivity for Hg2+ was attributed to the powerful affinity of highly electronegative chlorine and Hg2+. Moreover, XPS spectra demonstrated the interaction between chlorine and Hg2+. This work provides a new inspiration for applications in the targeted monitoring and removal of heavy metal pollution.

No abstract available

No abstract available

Toxic metals that are released into aquatic environments from natural and anthropogenic sources are absorbed by aquatic organisms and may threaten the health of both aquatic organisms and humans. Despite this, there have been limited studies on the metal concentrations in fish and humans in Central Asia. This study summarizes the presence of the toxic metals arsenic (As), mercury (Hg), cadmium (Cd), and lead (Pb) in aquatic bodies, fish, and seafood products and conducts a risk assessment. While certain areas show a notable increase in fish and seafood consumption, the overall intake in Central Asia remains below recommended levels. However, in regions with high fish consumption, there is a potential for elevated exposure to toxic metals, especially Hg. The risk of exposure to toxic metals in fish and seafood in Central Asia emerges as a significant concern. Comprehensive monitoring, regulation, and remediation efforts are imperative to ensure the safety of water sources and food consumption in the region. Public awareness campaigns and the establishment of dietary guidelines play a crucial role in minimizing the health risks associated with consumption.

South Africa stands out as a prominent global contributor of mercury (Hg) emissions, a matter of great concern due to its toxic nature and potential serious health effects on biota if it enters the environment. Mercury enters freshwater systems through various anthropogenic activities, such as emissions from coal-fired power stations and artisanal gold mining. Studies have indicated that bivalves accumulate metals from their aquatic environment. The freshwater bivalve genus Corbicula is widely distributed across South Africa and is relatively abundant. Given the widespread presence of Corbicula clams in South Africa, they have the potential to serve as bioindicators for Hg pollution in freshwater ecosystems. A total of 34 sites were sampled across the northeastern part of South Africa, with Corbicula clams found at 15 of these sites. At each site, a minimum of five clams were collected, alongside water and sediment samples. Total Hg (THg) concentrations were determined in sediment and clam samples using a flow injection mercury system. Total Hg concentrations in sediment samples correlated with different land-use activities, where sites closer to Hg sources had higher THg concentrations. This study also found higher environmental THg concentrations in the Olifants, and Inkomati Water Management Areas as reported 12 years ago. Clam THg concentrations were found to be higher than in the corresponding sediment samples, specifically in larger clams, suggesting longer Hg exposure at some sites. A weak positive correlation was found between sediment and clam THg concentrations, suggested that bioaccumulation may be influenced more by exposure period, rather than exposure concentrations. This study highlights the potential for these clams to serve as effective bioindicators since the accumulation of THg in their tissue can provide a better overview of the bioavailable THg in the aquatic system, compared to abiotic environmental samples alone.

The Atrato river basin was protected by Colombian law due to anthropogenic impacts, mainly from illegal gold mining, which triggered a critical environmental health problem. In this study we quantified mercury (Hg), methylmercury (MeHg) and arsenic (As) concentrations in aquatic environmental matrices, and explored for the first-time nuclear degenerations in fish from the Atrato River. The median concentrations (μg/kg) for T-Hg, MeHg and As in fish were 195.0, 175.5, and 30.0; in sediments (μg/kg) 165.5, 13.8 and 3.1; and in water (ng/L), 154.7 for T-Hg and 2.1 for As. A 38% and 10% of the fish exceeded the WHO limit for the protection of populations at risk (200 μg Hg/kg) and for human consumption (500 μg Hg/kg); while As concentrations were below the international standard (1000 μg/kg) in all fish. The percentage of MeHg was 89.7% and the highest accumulation was observed in carnivorous fish (336.3 ± 245.6 μg/kg, p < 0.05) of high consumption, indicating risk to human health. In water, T-Hg concentrations exceeded the threshold effect value of 12 ng/L, whereas As concentrations were below the threshold of 10,000 ng/L, established by USEPA. On the contrary, 33% of the sediments exceeded the quality standard of 200 μg/kg for Hg. We found that Prochilodus magdalenae was the species with the highest susceptibility to nuclear alterations in its order, nuclear bud (CNB, 3.7 ± 5.4%), micronuclei (MN, 1.6 ± 2.5%) and binucleated cells (BC, 1.6 ± 2.3%). These results indicate that the species appears to be a good predictor of genotoxicity in the Atrato River. Fulton's condition factor (K) indicated that 31.7% of the fishes had poor growth condition, suggesting that the Atrato river basin needs to be monitored and restored in accordance with the agreements reached in the Minamata Convention on Mercury.

Heavy metals are among the most important pollutants that threaten the aquatic environment when their concentrations exceed certain limits. Some of these metals and metalloids are beneficial and necessary for fish, but others, such as arsenic (As), chromium (Cr), cadmium (Cd), lead (Pb) and mercury (Hg), are non-essential and toxic. In reviewing the recent relevant literature, 4 different continents, 13 different countries, and more than 50 different fish species were analyzed in terms of As, Cr, Cd, Pb and Hg concentrations. According to the comparative results, it was found that in Tercan Dam Lake, Turkey, the highest concentration of Cr was detected in Capoeta umbla (2.455 mg/kg), and of As in Ctenopharyngodon idella (0.774 mg/kg) species. Greater values than the permissible limits of FAO/WHO in terms of As were also found in Andalusia, Southern Spain, in Mullus surmuletus (0.427 mg/kg), and Sardina pilchardus (0.561 mg/kg) and in Sprattus sprattus (0.636 mg/kg) in the Baltic Sea, but a remarkably high content of As (8.48 mg/kg) was determined in Penaeus notialis, found in Guinea, Africa. Moreover, Cd concentration was low to nil in almost all cases, with the exception of Amblyceps mangois species collected from the Dhaleshwari River in Bangladesh, which showed the highest value (0.063 mg/kg). Finally, extremely high levels of Pb were found in Plectropomus pessuliferus (5.05 mg/kg) and Epinephelus summana (2.80 mg/kg) in Jeddah, Saudi Arabia. The Hg content in fish was under the permissible limit in almost all cases, with megrim and red mullet from the Andalusian Sea exhibiting a relatively higher content (0.091 and 0.067 mg/kg). In general, the sequence of accumulation of toxic elements in fish was As > Cr > Pb > Cd > Hg.

Mercury (Hg) exists in different chemical forms presenting varied toxic potentials. It is necessary to explore an ecological risk assessment method for different mercury species in aquatic environment. The predicted no-effect concentrations (PNECs) for Hg(II) and methyl mercury (MeHg) in the aqueous phase, calculated using the species sensitivity distribution method and the assessment factor method, were 0.39 and 6.5×10(-3)μg/L, respectively. The partition theory of Hg between sediment and aqueous phases was considered, along with PNECs for the aqueous phase to conduct an ecological risk assessment for Hg in the sediment phase. Two case studies, one in China and one in the Western Black Sea, were conducted using these PNECs. The toxicity of mercury is heavily dependent on their forms, and their potential ecological risk should be respectively evaluated on the basis of mercury species.

Fish are a recommended component of the diet, supplying complete proteins, vitamins, mineral salts, and omega-3 fatty acids. The presence of mercury in fish tissue, both freshwater and marine, is the effect of its accumulation in the aquatic environment and depends largely on the concentration of mercury in water as well as food. Most of mercury in fish tissues is present in the form of organic complexes, mainly methylmer - cury, which is much more toxic than metallic mercury. In organisms of predatory fish, such as shark, tuna, swordfish, or eel, mercury will be present in concentrations higher than in other species of fish. It is not just the result of their nutrition, but is also related to their age, mobility and habitat. In fish living near the bot - tom of a water body, the concentration of mercury will be much higher. It has to be noted that the ongoing climate change and increase in environmental contamination may significantly raise the bioavailability of mercury and its organic complexes in

Mercury is a heavy metal that is extremely toxic. There are three types of it: inorganic, organic, and elemental. Mercury in all its forms has been shown to have harmful effects on living things. It can multiply its concentration from lower to higher trophic levels and accumulate in the body's various tissues. Aquatic organisms bodies have been exposed to mercury mostly through various human activities. The largest source of mercury pollution in the air is thermal power plants that mostly use coal as fuel. It is carried to a body of water after being deposited on the ground surface from the air. The way it enters the food chain is through aquatic plants and animals. Mercury accumulations in the kidney, liver, gills, or gonadal tissues of species that are readily exposed and ingested in aquatic organisms environments. There are possible effects of mercury exposure at both acute and long-term levels. The length of time, the mode of exposure, and the dosage all affect how harmful a substance is. The current study provides information about the harmful effects of mercury in aquatic organisms environments. Even though significant mitigation measures and recommendations were implemented, this assessment provides a comprehensive account of mercury sources and emissions, as well as their destiny and movement across the various environmental compartments. Because of the existing mercury emissions and stability, eating fish still poses a major risk. Aquatic life may be toxically affected by mercury pollution in freshwater environments. Through the food chain, mercury buildup in aquatic organisms can also endanger human health. Aquatic creatures include macroinvertebrates and fish. which people ingest and put their health at serious risk. The effect of mercury on hydrocarbons and how it enters the food chain to reach humans has been identified.

The intensification of anthropogenic activities has led to the widespread release of micropollutants, including mercury (Hg), into aquatic environments. Mercury is a persistent and hazardous contaminant with severe ecological and human health implications. Previous reviews have primarily examined mercury or microplastics (MPs) in isolation, but the novelty of this study lies in its focus on their co-exposure and combined impacts within aquatic food webs. Specifically, this review addresses the central research question: how do mercury and microplastics jointly influence bioaccumulation and ecotoxicological risks? To answer this, 92 peer-reviewed articles published since 2010 were systematically analyzed, with 58 % focusing on marine environments. A bibliometric analysis revealed a growing research emphasis on mercury-MP interactions, highlighting their emerging importance. Case data indicated extremely high mercury concentrations in the Agadir coastline, Morocco (up to 440 μg/L), while among fish species, Thunnus obesus (Bigeye tuna) and Rhaphiodon vulpinus exhibited the highest reported burdens (>6000 ng/g dry weight). Moreover, several studies documented a strong positive correlation (R2 = 0.68) between mercury levels in water and fish tissues. Collectively, these findings demonstrate the ecological risks posed by combined contaminant pathways and underscore the urgent need for comprehensive monitoring, regulatory measures, and policies to protect aquatic ecosystems and public health.

Phytoplankton are traditionally viewed as simple bioaccumulators and key entry points for mercury (Hg) into aquatic trophic chain. However the more recent findings suggest that they can function as dynamic biological systems capable of enhancing Hg cycling reactivity and altering its speciation. Nevertheless, the role of phytoplankton species in mercury transformations remains largely overlooked. The present study examined inorganic mercury (Hg(II)) methylation, monomethylmercury (MeHg) demethylation, and the production of dissolved gaseous mercury (Hg(0)) following exposure to sub-nanomolar concentrations Hg(II) or MeHg, representative of contaminated environments. Diatom Cyclotella meneghiniana was selected as a representative phytoplankton species due to its widespread presence in diverse aquatic ecosystems. To track transformation pathways, isotopically labeled Hg species were used to distinguish between methylation and demethylation processes. The results demonstrated rapid accumulation of both Hg(II) and MeHg in the diatom cells. A cellular demethylation of MeHg into Hg(II), primarily occurring within the cell debris fraction, but no detectable Hg(II) methylation was observed. The reduction of Hg(II) to Hg(0) was found to be biologically mediated and independent of the photosynthetic system. No significant production of Hg(0) after MeHg exposure was determined. Overall, these findings imply that phytoplankton species could actively contribute to mercury cycling in aquatic environments through cellular transformation processes, including MeHg demethylation and Hg(II) reduction.

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Gold mining activities influence the environment, mainly the aquatic environment, due to the heavy metal and mercury detected in settling pond and river waters. Based on laboratory analysis, it is known that Mercury concentrations in settling pond water of inlet, transition, and outlet zones respectively are 0.075 mg/L, 0.042 mg/L, and 0.027 mg/L. These are shown that mercury concentration in water was not passed Government Regulation of the Minister of Environment No. 202 the year 2004 about quality standards of liquid waste, which said that the standard is 0.005 mg/L. The Heavy metal concentrations, especially mercury in river water at 1, 2, 3, 4, and 5 stations respectively, are 0.004 mg/L, 0.009 mg/L, 0.050 mg/L, and 0.006 mg/L, which do not meet the government regulation of water quality standard 0.001 mg/L.

Mercury (Hg) is a ubiquitous contaminant in the environment and its methylated form, methylmercury (MeHg), poses a worldwide health concern for humans and wildlife, primarily through fish consumption. Global production of forest fire ash, derived from wildfires and prescribed burns, is rapidly increasing due to a warming climate, but their interactions with aqueous and sedimentary Hg are poorly understood. Herein, we compared the differences of wildfire ash with activated carbon and biochar on the sorption of aqueous inorganic Hg and sedimentary Hg methylation. Sorption of aqueous inorganic Hg was greatest for wildfire ash materials (up to 0.21 μg g-1 or 2.2 μg g-1 C) among all of the solid sorbents evaluated. A similar Hg adsorption mechanism for activated carbon, biochar made of walnut, and wildfire ash was found that involves the formation of complexes between Hg and oxygen-containing functional groups, especially the -COO group. Notably, increasing dissolved organic matter from 2.4 to 70 mg C L-1 remarkably reduced Hg sorption (up to 40% reduction) and increased the time required to reach Hg-sorbent pseudo-equilibrium. Surprisingly, biochar and wildfire ash, but not activated carbon, stimulated MeHg production during anoxic sediment incubation, possibly due to the release of labile organic matter. Overall, our study indicates that while wildfire ash can sequester aqueous Hg, the leaching of its labile organic matter may promote production of toxic MeHg in anoxic sediments, which has an important implication for potential MeHg contamination in downstream aquatic ecosystems after wildfires.

In urban and industrial regions, sedimentary mercury (Hg) serves as the crucial indicator for Hg pollution, posing potential risks to ecology and human health. The physicochemical processes of Hg in aquatic environments are influenced by various factors such as anthropogenic emissions and aquatic environmental impacts, making it challenging to quantify the drivers of total mercury (THg) variations. Here, we analyzed the spatiotemporal variations, quantified driving factors, and assessed accumulation risks of sedimentary THg from the mainstream of a typical urban river (Haihe River). THg in the urban region (37-3237 ng g-1) was significantly higher ( t test, p < 0.01) than in suburban (71-2317 ng g-1) and developing regions (156-916 ng g-1). The sedimentary THg in suburban and developing regions increased from 2003 to 2018, indicating the elevated atmospheric deposition of Hg. Together with the temperature, grain size of sediments, total organic carbon (TOC), the pH and salinity of water, 40 components of parent and substituted polycyclic aromatic hydrocarbons (PAHs) were first introduced to quantify the driver of sedimentary THg based on generalized additive model. Results showed that anthropogenic emissions, including three PAHs components (31%) and TOC (63%), accounted for 94% of sedimentary THg variations. The aquatic environmental impacts accounted for 5% of sedimentary THg variations. The geo-accumulation index of THg indicated moderate to heavy accumulation in the urban region. This study demonstrates that homologous pollutants such as PAHs can be used to trace sources and variations of Hg pollution, supporting their co-regulation as international conventions regulate pollutants.

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The ability of submerged aquatic plants (Elodea canadensis, Myriophyllum spicatum, Ceratophyllum demersum) and a natant plant (Eichhornia crassipes) to bioaccumulate mercury was evaluated in a laboratory experiment as well as in a real aquatic ecosystem situated in the vicinity of a cinnabar mine. Moreover, the ability of the diffusive gradients in the thin films technique (DGT) to predict mercury bioavailability for selected aquatic plants was tested. The submerged plants had sufficient bioaccumulation capacity for long-term phytoaccumulation of mercury in a real aquatic ecosystem. The determined bioaccumulation factor was greater than 1000. On average, the submerged plant leaves accumulated 13 times more mercury than the leaves of the natant aquatic plants. Chlorides at concentrations up to 200 mg/L had no statistically significant effect on mercury accumulation, nevertheless, the presence of humic acid in the water environment resulted in its significant (p < 0.002) decrease. A strong positive correlation (r > 0.66) was determined between mercury concentration in the input parts (leaves and/or roots) of the aquatic plants and the flow of mercury into DGT units.

The Minamata Convention to reduce anthropogenic mercury (Hg) emissions entered into force in 2017, and attention is now focused on how to best monitor its effectiveness at reducing Hg exposure to humans. A key question is how closely Hg concentrations in the human food chain, especially in fish and other aquatic wildlife, will track the changes in atmospheric Hg that are expected to occur following anthropogenic emission reductions. We investigated this question by evaluating several regional groups of case studies where Hg concentrations in aquatic biota have been monitored continuously or intermittently for several decades. Our analysis shows that in most cases Hg time trends in biota did not agree with concurrent Hg trends in atmospheric deposition or concentrations, and the divergence between the two trends has become more apparent over the past two decades. An over-arching general explanation for these results is that the impact of changing atmospheric inputs on biotic Hg is masked by two factors: 1) The aquatic environment contains a large inventory of legacy emitted Hg that remains available for bio-uptake leading to a substantial lag in biotic response time to a change in external inputs; and 2) Biotic Hg trends reflect the dominant effects of changes in multi-causal, local and regional processes (e.g., aquatic or terrestrial biogeochemical processes, feeding ecology, climate) that control the speciation, bioavailability, and bio-uptake of both present-day and legacy emitted Hg. Globally, climate change has become the most prevalent contributor to the divergence. A wide range of biotic Hg outcomes can thus be expected as anthropogenic atmospheric Hg emissions decline, depending on how these processes operate on specific regions and specific organisms. Therefore, evaluating the effectiveness of the Minamata Convention will require biomonitoring of multiple species that represent different trophic and ecological niches in multiple regions of the world.

Artisanal and small-scale gold mining (ASGM), energy production and other industrial inputs are a major source of anthropogenic mercury (Hg) to the aquatic environment globally, and these inputs have led to environmental contamination and human exposure. While studies have documented the effects of Hg inputs to rivers and marine waters of the West African region, estuarine waters of Cote d'Ivoire have been understudied, besides the waters surrounding Abidjan. To fill this gap, and to examine the potential for human exposure to methylmercury (MeHg), we measured the concentrations of total Hg, MeHg, and ancillary parameters in water (dissolved and particulate phases), sediment and fish to determine the extent of environmental impact and the potential for MeHg exposure for people consuming these fish. Levels of Hg and MeHg in sediment were elevated in the vicinity of the urban environment (up to 0.3 ng/g dry weight (dw) MeHg and 623 ng/g dw total Hg) and lowest in the more remote estuarine environments. Measurements of Hg in tuna and other larger pelagic coastal species indicated that levels were elevated but comparable to other North Atlantic regions. However, levels of Hg in fish, even smaller estuarine species, were such that the rural and urban populations are potentially being exposed to unsafe levels of MeHg, primarily as a result of the relatively high fish consumption in Cote d'Ivoire compared to other countries. Overall, both local point sources and the transport of Hg used in interior ASGM activities are the sources for Hg contamination to these coastal waters.

Although the introduction of non‐native fish species has been shown to alter trophic ecology in aquatic ecosystems, there has been limited research on how invasive species alter methylmercury (MeHg) biomagnification in lacustrine food webs. We sampled surface water and biota from 8 lakes in Quebec, Canada, spanning a range of dissolved organic carbon (DOC) concentrations (2.9–8.4 mg/L); 4 lakes were inhabited by native brook trout (Salvelinus fontinalis), and the remaining lakes contained brook trout and a non‐native fish, Allegheny pearl dace (Margariscus margarita). Periphyton, zooplankton, macroinvertebrates, and fish were analyzed for: 1) stable carbon (δ13C) and nitrogen (δ15N) isotope ratios to delineate food webs, and 2) total Hg (THg) or MeHg. Compared with the brook trout from reference lakes, fish from invaded lakes had higher length‐standardized THg concentrations as well as a narrower dietary range and elevated trophic level, inferred from unadjusted δ13C and δ15N values, respectively. The rate of Hg biomagnification was similar across invaded and reference lakes, implying little effect of the invasive fish on the trophic transfer of MeHg. Despite differences in food web structure due to pearl dace invasion, DOC was the strongest predictor of brook trout THg levels for all lakes, suggesting that underlying environmental factors exerted a stronger influence on brook trout THg concentrations than the presence of a non‐native forage fish. Environ Toxicol Chem 2020;39:2196–2207. © 2020 SETAC

Prey composition and availability is considered a primary predictor of Lake Trout (Salvelinus namaycush) mercury (Hg) concentrations. Evidence from other freshwater fishes suggests that environmental and landscape factors likely also contribute to fish Hg dynamics, yet comprehensive, contemporary assessments for Lake Trout from boreal and north-temperate lakes are lacking. Here, we reassess the importance of prey characteristics using both previously published and contemporary data, incorporating additional variables and model complexity to better understand factors influencing Hg dynamics of Ontario Lake Trout. Our analyses indicate that 1) Lake Trout Hg concentrations are primarily associated with individual body size, 2) high dissolved organic carbon (DOC) concentrations elevate Hg for fish of a given size, and 3) a coarse categorization of food chain length, specifically the presence of Mysis diluviana, informs Hg biomagnification slopes. The inclusion of DOC was vital for assessing human consumption risk, as Lake Trout in high DOC lakes were more likely to exceed Hg guidelines at sizes often harvested by anglers. Drivers of Lake Trout Hg levels in boreal and north-temperate lakes closely match those reported to affect other fishes in the region, regardless of feeding, thermal, and habitat strategies.

The Three Gorges Reservoir (TGR) holds the distinction of being China's largest reservoir, and the presence of pollutants in the fish from the reservoir have a direct impact on the health of local residents. Thus, 349 fish specimens of 21 species and 1 benthos (Bellamya aeruginosas) were collected from four typical tributaries of the TGR from 2019 to 2020. These specimens were analyzed for the concentrations of total mercury (THg) and methylmercury (MeHg), and some representative samples were tested for δ13C and δ15N values to reveal the characteristics of bioaccumulation and biomagnification. The maximum safe daily consumption was estimated based on the oral reference dose (0.1 μg kg-1 bw/day according to US-EPA, 2017). The results showed that the mean THg and MeHg concentrations in fish from the TGR tributaries were 73.18 ± 49.21 ng g-1 and 48.42 ± 40.66 ng g-1, respectively, with the trophic magnification factors (TMFs) of THg and MeHg being 0.066 and 0.060, respectively. Among all the fish species in the tributaries, the highest daily maximum safe consumption amount was 1253.89 g for S. asotus consumed by adults, while the lowest was 62.88 g for C. nasus consumed by children.

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Mercury biomagnification in aquatic ecosystems is a global issue. Biomagnification patterns and drivers in alpine regions remain poorly understood. Hg biomagnification in the aquatic food web of the Qinghai-Tibetan Plateau (Q-T Plateau) was investigated. A total of 302 fish and macroinvertebrate tissue samples were analysed for total mercury (THg) and nitrogen (δ15N) stable isotope ratios. Overall, 26.75% of fish individuals exceeded the USFWS consumption guidelines. A total of 52.17% of the sampling sites covering different habitats exhibited a significantly positive THg-δ15N relationship, which confirmed the Hg biomagnification potential of Q-T Plateau aquatic ecosystems. The Q-T Plateau Hg biomagnification rates were generally far higher than global averages regardless of the habitat type. Hg in sediments, elevation and population density were positively related to the Hg biomagnification magnitude on the Q-T Plateau, which could be attributed to the disproportionate response of Hg concentrations in macroinvertebrates and fishes along environmental gradients. Our findings offer empirical evidence that fish consumption on the Q-T Plateau poses a substantial Hg exposure risk to people living along river and lake shores. Higher biomagnification rates could further disproportionately accelerate Hg pollution in Q-T Plateau aquatic ecosystems under future anthropogenic activities and climate warming trajectories.

Despite a global phase out of some point sources, mercury (Hg) remains elevated in aquatic food webs, posing health risks for fish-eating consumers. Many tropical regions have fast growing organisms, potentially short food chains, and few industrial point sources, suggesting low Hg baselines and low rates of trophic magnification with limited risk to people. Nevertheless, insufficient work on food-web Hg has been undertaken in the tropics and fish consumption is high in some regions. We studied Hg concentrations in fishes from floodplain lakes of the Juruá River, Amazonas, Brazil with three objectives: 1) determine rates of Hg trophic magnification, 2) assess whether Hg concentrations are high enough to impact humans eating fish, and 3) determine whether there are seasonal differences in fish Hg concentrations. A total of 380 fish-muscle samples were collected from 12 floodplain lakes during the low-water (September 2018) and falling-water (June 2019) seasons and analysed for total Hg and stable nitrogen (N) isotopes. The average trophic magnification factor (increase per trophic level) was 10.1 in the low-water season and 5.4 in the falling-water season, both well above the global average for freshwaters. This high rate of trophic magnification, coupled with higher-than-expected Hg concentrations in herbivorous species, led to high concentrations (up to 17.6 mg/kg dry weight) in predatory pirarucu and piranha. Nearly 70% of all samples had Hg concentrations above the recommended human-consumption guidelines. Average concentrations were 42% higher in the dry season than the wet season, but differences varied by species. Since Hg concentrations are higher than expected and fish consumption in this region is high, future research should focus on Hg exposure for human populations here and in other tropical-rainforest regions, even in the absence of local point sources of Hg.

Mercury (Hg) is a global pollutant of concern because its organic and more toxic form, methylHg (MeHg), bioaccumulates and biomagnifies through aquatic food webs to levels that affect the health of fish and fish consumers, including humans. Although much is known about trophic transfer of MeHg in aquatic food webs at temperate latitudes in the northern hemisphere, it is unclear whether its fate is similar in biota from coastal zones of the southeastern Pacific. To assess this gap, MeHg, total Hg and food web structure (using δ13C and δ15N) were measured in marine macroinvertebrates, fishes, birds, and mammals from Patagonian fjords and the Antarctic Peninsula. Trophic magnification slopes (TMS; log MeHg versus δ15N) for coastal food webs of Patagonia were high when compared with studies in the northern hemisphere, and significantly higher near freshwater inputs as compared to offshore sites (0.244 vs 0.192). Similarly, in Antarctica, the site closer to glacial inputs had a significantly higher TMS than the one in the Southern Shetland Islands (0.132 vs 0.073). Composition of the food web also had an influence, as the TMS increased when mammals and seabirds were excluded (0.132-0.221) at a coastal site. This study found that both the composition of the food web and the proximity to freshwater outflows are key factors influencing the TMS for MeHg in Patagonian and Antarctic food webs.

As the dominant mercury species in fish, methylmercury (MeHg) biomagnifies during its trophic transfer through aquatic food webs. MeHg is known to bind to cysteine, forming the complex of MeHg-cysteine. However, relationship between MeHg and cysteine in large-scale food webs has not been explored and contrasted with MeHg biomagnification models. Here, we quantified the compound-specific nitrogen isotopic analysis of amino acids (CSIA-AA), MeHg, and amino acid composition in aquatic organisms of Poyang Lake, the largest freshwater lake in China. The trophic positions (TPAA) of organisms ranged from 1.0 ± 0.1-3.7 ± 0.2 based on CSIA-AA approach. The trophic magnification factor (TMF) of MeHg, derived from the regression slope of Log-transformed MeHg in organisms upon their TPAA for the entire food web was 9.5 ± 0.5. Significantly positive regression between MeHg and cysteine (R2 = 0.64, p < 0.01) was documented, suggesting MeHg-cysteine complex may potentially play a critical role in the bioaccumulation of MeHg. Furthermore, TMFs of MeHg calculated with and without cysteine normalization compared well (7.7-8.7) when excluding primary producers. Our results implied that MeHg may biomagnify as the complex of MeHg-cysteine and contribute to our understanding of MeHg trophic transfer at the molecular level.

Species traits and trophic interactions drive contaminant flux and fate in linked river-riparian food webs. Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator resistant and a trophic dead end for Hg in food webs we studied. Fishes preferred blackflies, which accounted for 56 to 80% of Hg flux to fishes, even where blackflies were rare. Food web properties, i.e., match/mismatch between insect production and fish consumption, governed amounts of Hg retained in the river versus exported to land. An experimental flood redistributed Hg fluxes in the simplified tailwater food web, but not in complex downstream food webs. Recognizing that species traits, species interactions, and disturbance mediate contaminant exposure can improve risk management of linked aquatic-terrestrial ecosystems.

Timber harvest has many effects on aquatic ecosystems, including changes in hydrological, biogeochemical, and ecological processes that can influence mercury (Hg) cycling. Although timber harvest's influence on aqueous Hg transformation and transport are well studied, the effects on Hg bioaccumulation are not. We evaluated Hg bioaccumulation, biomagnification, and food web structure in 10 paired catchments that were either clear-cut in their entirety, clear-cut except for an 8-m wide riparian buffer, or left unharvested. Average mercury concentrations in aquatic biota from clear-cut catchments were 50% higher than in reference catchments and 165% higher than in catchments with a riparian buffer. Mercury concentrations in aquatic invertebrates and salamanders were not correlated with aqueous THg or MeHg concentrations, but rather treatment effects appeared to correspond with differences in the utilization of terrestrial and aquatic basal resources in the stream food webs. Carbon and nitrogen isotope data suggest that a diminished shredder niche in the clear-cut catchments contributed to lower basal resource diversity compared with the reference of buffered treatments, and that elevated Hg concentrations in the clear-cut catchments reflect an increased reliance on aquatic resources in clear-cut catchments. In contrast, catchments with riparian buffers had higher basal resource diversity than the reference catchments, indicative of more balanced utilization of terrestrial and aquatic resources. Further, following timber harvest THg concentrations in riparian songbirds were elevated, suggesting an influence of timber harvest on Hg export to riparian food webs. These data, coupled with comparisons of individual feeding guilds, indicate that changes in organic matter sources and associated effects on stream food web structure are important mechanisms by which timber harvest modifies Hg bioaccumulation in headwater streams and riparian consumers.

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Algal density can significantly impact mercury (Hg) bioaccumulation and biomagnification in aquatic food webs, but the underlying mechanisms remain controversial especially in subtropical and tropical regions. We conducted a comprehensive field study on Hg bioconcentration in phytoplankton and bioaccumulation in size-fractionated zooplankton across 17 sampling sites in Lake Taihu, a large shallow lake in eastern China with large spatial differences in algal density. The higher algal density in the northern sites is highly associated with the lower THg bioconcentration factor (BCF) in phytoplankton and lower THg bioaccumulation factor (BAF) in zooplankton. The low Hg BCFs or BAFs at productive sites could not be explained by algal bloom dilution but attributed to the low Hg bioavailability, which is highly associated with the elevated pH levels at productive sites. The smaller body size of the dominant zooplankton species at higher algal density sites also contributed to their lower Hg bioaccumulation. Importantly, we provide evidence that high algal density is associated with a low proportion of methylmercury (MeHg) in total Hg (% MeHg) in phytoplankton, which is further transferred to zooplankton. Such a low THg BCF or BAF and low % MeHg in plankton at high algal density sites hamper the entry of Hg into the pelagic food webs, which are important but yet underestimated driving forces for the low Hg contents in pelagic fish that are commonly observed in anthropogenic-impacted eutrophic lakes in subtropical regions.

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Biomagnification of environmental toxins is influenced by food chain length, which in turn is shaped by habitat connectivity and food web dynamics. Dam removals are increasingly used as restoration measures, yet their role in reducing contaminant exposure has rarely been quantified. We tested if mercury concentration in pike ( Esox lucius ) muscle tissue was reduced by removals of lake outlet dams in five oligotrophic, boreal lakes, using a before‐after design. For pike of average size (50 cm), mean mercury concentration decreased from 843 to 598 μg Hg per kg muscle tissue following dam removal, which corresponds to a 29% reduction. These results show that dam removal can lower mercury bioaccumulation in apex predators, providing an additional conservation benefit of restoring natural aquatic connectivity, with positive implications for both ecosystem integrity and human health.

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The bioaccumulation of methylmercury (MeHg) within the pelagic food webs is a crucial determinant of the MeHg concentration in the organisms at higher trophic levels. Dissolved organic matter (DOM) is recognized for its influence on mercury (Hg) cycling in the aquatic environment because of its role in providing metabolic substrate for heterotrophic organism and serving as a strong ligand for MeHg. However, the impact of DOM on MeHg bioaccumulation in pelagic food chains remain controversial. Here, we explored MeHg bioaccumulation within a pelagic food web in China, in the eutrophic Bohai Sea and adjacent seas, covering a range of DOM concentrations and compositions. Our findings show that elevated concentrations of dissolved organic carbon (DOC) and phytoplankton biomass may contribute to a reduction in MeHg uptake by phytoplankton. Moreover, we observe that a higher level of autochthonous DOM in the water may result in more significant MeHg biomagnification in zooplankton. This can be explained by alterations in the structure of pelagic food webs and/or an increase in the direct consumption of DOM and particulate organic matter (POM) containing MeHg. Our study offers direct field monitoring evidence of dual roles played by DOM in regulating MeHg transfers from water to phytoplankton and zooplankton in coastal pelagic food webs. A thorough understanding of the intricate interactions is essential for a more comprehensive evaluation of ecological risks associated with MeHg exposure in coastal ecosystems.

Seasonality characterises northern latitude lakes, however, limited knowledge exists regarding seasonal fluctuations in mercury (Hg) biomagnification. This study tested for these fluctuations year-round in the food web of a boreal humic lake (Lake Pääjärvi, in southern Finland) and for differences between two methods of trophic level (TL) determination. A food web sample was collected in three open-water seasons and one ice-covered season. TL was calculated using bulk nitrogen stable isotopes (δ15N) and compound-specific stable isotope analysis of δ15N in amino acids (CSIA-AA). Biomagnification of total Hg (THg), measured through the linear regression of THg (log10[THg]) and TLs, was detected in all seasons using both isotope methods. No significant differences in seasonal trophic magnification slope (TMS), the slope of the linear regression, in- and between methods were found. However, [THg] baseline estimates, the intercept of the linear regression, were significantly different between methods when comparing the same seasons. [THg] baseline values were generally higher in all seasons in bulk δ15N than CSIA-AA. Results highlight relatively stable biomagnification among seasons in both methods, however, direct comparisons of bulk δ15N and CSIA-AA TLs require further methodological development.

Lebo Taliwang Lake has been reported to be polluted by mercury compounds. This study aims to determine the occurrence of mercury biomagnification in the food chain in Lebo Lake Taliwang. Samples of water, tilapia, water strider and japan pond heron were taken at two sampling locations: inlet and outlet. Samples were tested for mercury content with a mercury analyzer. The results show that there is mercury accumulation in the Lebo Taliwang Lake ecosystem. The average of each sample was 1.95 in water, 99.5 in tilapia, 79.8 in water srider, and 948.09 and 143 in feathers and blood, respectively. Furthermore, the results of the biomagnification factor (BMF) value show the BMF>1. This means that there is biomagnification of mercury in Lebo Taliwang Lake. The biomagnification value of japan pond heron in feather and blood with nile tilapia is 9.52 and 1.43. Meanwhile, with water stider, the values are 11.87 and 1.81. This study recommends enhanced monitoring and regulation of illegal gold mining (PETI) activities, as well as environmental rehabilitation efforts around Lake Lebo

Freshwater ecosystems are among the most important ecosystems worldwide, however, over the last centuries, anthropogenic pressures have had catastrophic effects on them. Mercury (Hg) is one of the main environmental contaminants which globally affect ecosystems and particularly freshwater wildlife. While Hg originates from natural sources, anthropogenic activities such as agriculture, biomass combustion, and gold mining increase its concentrations. Gold mining activities are the main drivers of Hg emission in tropical ecosystems and are responsible for up to 38% of global emissions. Once in its methylated form (MeHg), mercury biomagnifies through the trophic chain and accumulates in top predators. Due to the toxicity of MeHg, long-lived predators are even more subjected to chronic effects as they accumulate Hg over time. In the present study we quantified Hg contamination in two top predators, the Black caiman Melanosuchus niger and the Agami heron Agamia agami, and in their prey in the Kaw-Roura Nature Reserve in French Guiana and evaluated the biomagnification rate in the trophic chain. Our results show that despite a TMF in the range of others in the region (4.38 in our study), top predators of the ecosystem present elevated concentrations of Hg. We have found elevated Hg concentrations in the blood of adult Black caiman (2.10 ± 0.652 μg g−1 dw) and chicks of Agami heron (1.089 ± 0.406 μg g−1 dw). These findings highlight the need to better evaluate the potential impact of Hg in freshwater top predators, especially regarding reprotoxic effects.

Methylmercury is a toxin of local, regional, and global concern, with estuarine habitats possessing ecological characteristics that support conversion of inorganic mercury into this methylated form. We monitored Hg concentrations in species within the food web of the lower Cape Fear River (CFR) estuary in 2018-2020. Samples were analyzed for Hg concentrations and nitrogen isotopes (a measure of trophic level), and we found a positive relationship within this food web each year (p < 0.0001), indicating biomagnification is occurring. The highest Hg concentrations were among the upper trophic level species (Royal Terns, 4.300 ppm). While the Hg concentrations we documented are below assumed thresholds for toxic effects, we found spikes in Hg concentrations after Hurricane Florence in 2018 and with other disturbances to the CFR that resuspended bottom sediments. Continued monitoring is needed to understand the cause of annual variations, health implications, and conservation needs.

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Although many attempts have been carried out to elaborate trophic magnification factor (TMF) and biomagnification factor (BMF), such as normalizing the concentration of pollutants and averaging diet sources, the uncertainty of the indexes still need to be improved to assess the bioaccumulation of pollutants. This study first suggests an improved BMF (i.e., BMF') applied to mercury bioaccumulation in freshwater fish from four sites before and after rainfall. The diet source and TP of each fish were identified using nitrogen stable isotope of amino acids (δ15NAAs) combined with bulk carbon stable isotope (δ13C). The BMF' was calculated normalizing with TP and diet contributions derived from MixSIAR. The BMF' values (1.3-27.2 and 1.2-27.8), which are representative of the entire food web, were generally higher than TMF (1.5-13.9 and 1.5-14.5) for both total mercury and methyl mercury, respectively. The BMF' implying actual mercury transfer pathway is more reliable index than relatively underestimated TMF for risk assessment. The ecological approach for BMF calculations provides novel insight into the behavior and trophic transfer of pollutants like mercury.

Mercury exists in three forms: elemental, inorganic, and organic, with methylmercury (MeHg) being the most concerning due to its ability to cross cellular barriers and bioaccumulate, particularly in marine mammals, where over 90 % of total mercury is in the MeHg form. Despite its importance, there is limited data on mercury bioaccumulation in marine mammals and maternal transfer mechanisms in the Southern Hemisphere. Pinnipeds, as ocean sentinels, are valuable for monitoring contaminants due to their ecological and biological traits. This study investigates mercury burdens and maternal transfer of mercury in South American sea lions (SASL) and South American fur seals (SAFS). Samples of clots and vibrissae from SASL pups and clots and milk from SAFS pups and females were analyzed. Total mercury (THg) levels in SASL ranged from 8.36 to 305.43 μg/Kg w.w. in clots and from 3071.8 to 28,034.5 μg/Kg d.w. in vibrissae. In SAFS, THg levels in clots ranged from 0.40 to 358.77 μg/Kg w.w. and in milk from 3.4 to 14.1 μg/Kg w.w. Significant differences were observed between newborn pups of both species, with a positive correlation between THg levels in clots from SAFS pups and females and between clots and vibrissae in SASL pups, indicating maternal transfer during gestation. Additionally, THg levels in SAFS pups decreased over time, suggesting biodilution. These species allow us to have a long term monitoring in both colonies and two different areas in Chile and are relevant findings to food security and the treatment of heavy metal contamination.

Simple Summary Lead (Pb) and mercury (Hg) are two of the major heavy metals of antiquity and have gained considerable importance as potent pollutants in aquatic environments. It is known that fish embryos or larvae are more sensitive to the monitoring of heavy metal contamination. Thus, RNA sequencing (RNA-seq) analysis based on physiological changes in larval zebrafish was conducted to investigate the toxic mechanisms of lead or mercury in fish during early life stages. Our results showed that acute lead exposure significantly decreased survival but increased the malformation rates of developing zebrafish from 48 hpf to 120 hpf. Transcriptomic analysis revealed that lead-triggered biological processes included cellular process, metabolic process, biological regulation, and response to stimulus. The most enriched lead-regulated pathways included cytochrome P450, glutathione metabolism, and lipid metabolism. Moreover, a series of differentially expressed genes (DEGs) were identified by both mercury and lead treatment, which could be useful for searching potential molecular markers against the evaluation of heavy metals contamination. Abstract This study was first conducted to investigate the effects of acute lead exposure on developing zebrafish embryos or larvae from 24 to 120 h post-fertilization (hpf). Our data showed that treatment with 50–200 μM lead significantly affected larval survivability and morphology compared to the respective control. Second, we chose 120 hpf larvae treated with 12.5 μM lead for RNA sequencing due to its exposure level being sufficient to produce toxic effects with minimum death and lead bioaccumulation in developing zebrafish. A total of 137.45 million raw reads were obtained, and more than 86% of clean data were mapped to the zebrafish reference genome. Differential expression profiles generated 116 up- and 34 down-regulated genes upon lead exposure. The most enriched GO terms for representative DEGs were ion transport and lipid metabolism. Third, a comparison with the dataset of mercury-regulated gene expression identified 94 genes (64 up-regulated and 30 down-regulated) for exposure specific to lead, as well as 422 genes (338 up-regulated and 84 down-regulated) for exposure specific to mercury. In addition, 56 genes were co-regulated by micromolar mercury and lead treatment, and the expression of thirteen genes, including mt2, ctssb.1, prdx1, txn, sqrdl, tmprss13a, socs3a, trpv6, abcb6a, gsr, hbz, fads2, and zgc:92590 were validated by qRT-PCR. These genes were mainly associated with metal ion binding, proteolysis, antioxidant activity, signal transduction, calcium ion or oxygen transport, the fatty acid biosynthetic process, and protein metabolism. Taken together, these findings help better understand the genome-wide responses of developing zebrafish to lead or mercury and provide potential biomarkers for acute exposure to toxic metals.

Mercury (Hg) is a widespread and toxic environmental contaminant. It is challenging to determine the level of Hg contamination of food chains and fish within the millions of water bodies in the United States. Mercury contamination can vary 10‐fold between ecosystems, even those in the same region. Therefore, aquatic ecosystems need to be individually monitored for Hg contamination to determine which ecosystems are most contaminated and pose the greatest risk to human and wildlife health. One approach to monitoring Hg is to use sentinel species, defined as biological monitors that accumulate a contaminant in their tissues without significant adverse effects. Riparian spiders such as long‐jawed orb weavers (Tetragnathidae) have been proposed as sentinels of persistent bioavailable contaminants, like Hg, in aquatic systems. Long‐jawed orb weavers feed on emergent aquatic insects and have concentrations of Hg that reflect levels of Hg contamination in the aquatic food web. Previous studies have documented elevated contaminant concentrations in long‐jawed orb weavers from shorelines of aquatic ecosystems, suggesting that they could be used as sentinels of chemical contaminants in aquatic ecosystems. We demonstrate for the first time that long‐jawed orb weavers can be used as sentinels to identify aquatic systems that contain fish with elevated concentrations of Hg. Environ Toxicol Chem 2022;41:1297–1303. © 2022 SETAC

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The presence of heavy metals in surface water bodies represents a significant threat to the health of aquatic ecosystems and the human populations that depend on them. This study determined the concentrations of mercury (Hg), copper (Cu), selenium (Se), barium (Ba), aluminum (Al), cobalt (Co), zinc (Zn), and chromium (Cr) at five sampling points located in the Cutuchi and Pumacunchi rivers, within the micro-watersheds of Cotopaxi Province, Ecuador. Laboratory-based physicochemical analyses were conducted, along with the calculation of the Heavy Metal Pollution Index (HPI) and the Andean Biological Index (ABI), based on benthic macroinvertebrate assessments. The results revealed concerning concentrations of certain metals such as Cu, Al, and Cr, particularly in areas with high anthropogenic activity, compromising water quality for domestic, agricultural, and livestock use. Monitoring programs and remediation strategies are recommended to preserve ecological functionality and reduce public health risks.

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The development of practical fluorescent probe for detecting toxic mercury ions (Hg2+) is desirable for environmental assurance and public health. In this study, a new red emissive fluorescent probe (KJL) was designed and synthesized for monitoring trace Hg2+ both in vitro and in vivo with distinct features including ideal response rate (within 4 min), red emission (596 nm), large Stokes shift (162 nm), highly sensitivity (LOD = 4.79 nM) and excellent specificity. KJL also validated the good capability for accurately monitoring trace Hg2+ levels in actual samples (faucet water, drinking water, river water, lake water, urine and serum) and possessed the eye-catching ability in visualization of Hg2+ under environmental/biological conditions, which revealed the great potential of this red-emitting fluorescent probe for practical applications in complex environmental and biological systems.

No abstract available

Atmospheric mercury (Hg) emissions and subsequent transport and deposition are major concerns within protected lands, including national parks, where Hg can bioaccumulate to levels detrimental to human and wildlife health. Despite this risk to biological resources, there is limited understanding of the relative importance of different Hg sources and delivery pathways within the protected regions. Here, we used Hg stable isotope measurements within a single aquatic bioindicator, dragonfly larvae, to determine if these tracers can resolve spatial patterns in Hg sources, delivery mechanisms, and aquatic cycling at a national scale. Mercury isotope values in dragonfly tissues varied among habitat types (e.g., lentic, lotic, and wetland) and geographic location. Photochemical-derived isotope fractionation was habitat-dependent and influenced by factors that impact light penetration directly or indirectly, including dissolved organic matter, canopy cover, and total phosphorus. Strong patterns for Δ200Hg emerged in the western United States, highlighting the relative importance of wet deposition sources in arid regions in contrast to dry deposition delivery in forested regions. This work demonstrates the efficacy of dragonfly larvae as biosentinels for Hg isotope studies due to their ubiquity across freshwater ecosystems and ability to track variation in Hg sources and processing attributed to small-scale habitat and large-scale regional patterns.

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Whole-cell biosensors could serve as eco-friendly and cost-effective alternatives for detecting potentially toxic bioavailable heavy metals in aquatic environments. However, they often fail to meet practical requirements due to an insufficient limit of detection (LOD) and high background noise. In this study, we designed a synthetic genetic circuit specifically tailored for detecting ionic mercury, which we applied to environmental samples collected from artisanal gold mining sites in Peru. We developed two distinct versions of the biosensor, each utilizing a different reporter protein: a fluorescent biosensor (Mer-RFP) and a colorimetric biosensor (Mer-Blue). Mer-RFP enabled real-time monitoring of the culture’s response to mercury samples using a plate reader, whereas Mer-Blue was analysed for colour accumulation at the endpoint using a specially designed, low-cost camera setup for harvested cell pellets. Both biosensors exhibited negligible baseline expression of their respective reporter proteins and responded specifically to HgBr2 in pure water. Mer-RFP demonstrated a linear detection range from 1 nM to 1 μM, whereas Mer-Blue showed a linear range from 2 nM to 125 nM. Our biosensors successfully detected a high concentration of ionic mercury in the reaction bucket where artisanal miners produce a mercury–gold amalgam. However, they did not detect ionic mercury in the water from active mining ponds, indicating a concentration lower than 3.2 nM Hg2+—a result consistent with chemical analysis quantitation. Furthermore, we discuss the potential of Mer-Blue as a practical and affordable monitoring tool, highlighting its stability, reliance on simple visual colorimetry, and the possibility of sensitivity expansion to organic mercury.

In the aquatic environments, heavy metal pollution remains a major challenge across the world since the metals of cadmium, lead, chromium, and mercury are toxic, persistent, and bioaccumulative. Traditional remediation mechanisms such as chemical precipitation, membrane filtration and adsorption can be costly to operate, produce secondary pollutants and are not adaptable to changing environmental conditions. The paper describes a new, integrated approach that will involve bio-engineering of microbial systems alongside a network of IoT to monitor the environment in order to implement intelligent, effective and scalable heavy metal cleanup in water bodies. Modifications to biosorption, bioaccumulation, redox conversion, and metal precipitation of engineered microbial strains to increase metal-responsiveness: engineered strains of Pseudomonas putida, Shewanella oneidensis, Ralstonia metallidurans and metal-binding cyanobacteria were developed by incorporating metal-responsive genetic circuits, observation of metallothionein overexpression and optimization of electron transfer pathways. To make these engineered microbes immobile to guarantee stability and reusability and biocontainment, there was use of sophisticated encapsulation matrices. Refining on the biological system, a distributed IoT network had been implemented with electrochemical heavy metal sensors and environmental probes, to allow real-time and continuous monitoring of the combinations of metal concentrations, pH, temperature, and dissolved oxygen. Machine learning models have been used to identify data sent over low-power communication protocols to predict contamination variation and autonomously control microbial deployment in response to controlled biocapsule release mechanisms. The outcome of prototype simulations and controlled experiments in microcosm showed that the integrated system was able to yield much better efficiencies of metal removal improvements of 25 to 60 percent over the wild-type strains, which held up to reasonable functional stability when faced with variation of environmental conditions. The integrated biological and digital system provides a strong platform to the future, autonomous remediation systems that can intelligently react to contamination dynamics. The study provides a basis of scalable self-regulating environmental biotechnical systems that could be implemented in rivers, lakes, industrial effluents and other susceptible water environment to solve the age-old issues of heavy metal pollution.

Understanding variations in total mercury (T-Hg) levels in fish is crucial for protecting aquatic biota and human health. This article evaluates the influence of environmental factors (temperature, pH) and biological variables (feeding habits, trophic level, total length, total weight), on T-Hg concentrations in fish from the Atrato River basin, Colombia. Utilizing a robust secondary data set of 842 fish samples from 16 species collected in 2019, we conducted a comprehensive analysis of these influences. We examined differences in T-Hg accumulation rates by habitat type (pelagic, benthopelagic and demersal) and probabilistically classified species based on their feeding habits and trophic levels. Our analysis identified a hierarchy of variables influencing T-Hg levels: feeding habits > total length > estimated total weight > trophic level > water temperature > pH, with temperature being the only predictor exerting a negative influence. Together, these variables accounted for over 60% of the variability in T-Hg accumulation in fish muscle tissue. Furthermore, fish in the Atrato River exhibited differential T-Hg based on habitat type, grouping into three distinct subpopulations stratified by feeding habits and trophic levels. These findings suggest that observed T-Hg accumulation patterns are driven by the functional ecology of the organisms, phenological characteristics, metabolism, contamination patterns, biogeography, land use, and the spatial and chemical configuration of the environmental matrices of the basin. Our results emphasize the importance of understand how biological and environmental factors influence T-Hg concentrations in fish, as these factors vary across aquatic systems. This knowledge is crucial for developing effective biodiversity management strategies. While we used a machine learning approach to identify key predictors of T-Hg accumulation, we also caution against potential biases in modeling T-Hg concentrations for aquatic biota management.

In the southeast and east coasts of the Republic of Korea, it is essential to monitor mercury accumulation in coastal organisms in view of the higher mercury distribution in sediments and human samples. However, mercury pollution monitoring in organisms, especially higher trophic-level organisms that can exhibit high mercury accumulation, is limited. Here, we examined the applicability of the eggs of the black-tailed gull (Larus crassirostris), which belongs to a high trophic level, for mercury monitoring in coastal areas. Breeding sites were selected in West, Southeast, and East Seas with different mercury concentrations in other matrices (sediment and biological samples of residents). The 5-year mean total mercury concentration in eggs collected during the breeding seasons from 2016 to 2020 was lower in Baengnyeongdo (705 ± 81 ng/g dry weight (dry), West Sea) than in Hongdo (1,207 ± 214 ng/g dry, Southeast Sea) and Ulleungdo (1,095 ± 95 ng/g dry, East Sea). The different patterns of mercury concentration in gull eggs among the breeding sites was consistent with those in the other matrices among the coastal areas. These results support the applicability of the black-tailed gull egg as an indicator for establishing a monitoring framework in the coastal areas of the Republic of Korea.

Aquatic plants are essential indicators of the environmental health of aquatic systems because of their sensitivity and vulnerability. They are also helpful for evaluating water quality in aquatic systems. This research examined the use of macrophytes and phytoplankton as biological indicators of differences in nutrient concentrations, heavy metals, and organic contaminants in freshwater and coastal ecosystems. Evaluating aquatic vegetation provides indications of eutrophication, pollution, and habitat changes through species composition, abundance, and physiological response. This study incorporates biological indicators with laboratory analysis of physicochemical water samples to determine how aquatic plant indicators relate to dissolved oxygen, pH, turbidity, and nutrient concentration. This study emphasizes the need to identify aquatic plant indicators that exhibit variability, as this aspect could have important implications for ecosystem monitoring. Investigation revealed that particular aquatic plant species exhibited morphological and biochemical variation under pollution-stress conditions, including Eichhornia crassipes (water hyacinth) and Lemna minor (duckweed). The study highlights the potential of aquatic plants and their indicators as inexpensive, sustainable, and ecologically relevant biological indicators, enabling long-term environmental monitoring and resource management. Finally, the use of aquatic plant-based biological indicators provides a means of ecosystem monitoring. Still, it has potential implications for environmental policy development and spatially and temporally based conservation efforts that maintain water quality and biodiversity in aquatic ecosystems.

No abstract available

Mercury is a highly toxic element present in water, soil, air, and biota. Anthropogenic activities, such as burning fossil fuels, mining, and deforestation, contribute to the presence and mobilization of mercury between environmental compartments. Although current research on mercury pathways has advanced our understanding of the risks associated with human exposure, limited information exists for remote areas with high diversity of fauna, flora, and indigenous communities. This study aims to deepen our understanding of the presence of total mercury in water, sediments, and fish, within aquatic ecosystems of two indigenous territories: Gomataon (Waorani Nationality) and Sinangoé (Ai´Cofán Nationality) in the Ecuadorian Amazon. Our findings indicate that, for most fish (91.5%), sediment (100%) and water (95.3%) samples, mercury levels fall under international limits. For fish, no significant differences in mercury levels were detected between the two communities. However, eight species exceeded recommended global limits, and one surpassed the threshold according to Ecuadorian legislation. Piscivore and omnivore fish exhibited the highest concentrations of total mercury among trophic guilds. Only one water sample from each community’s territory exceeded these limits. Total mercury in sediments exhibited greater concentrations in Gomataon than Sinangoé. Greater levels of mercury in sediments were associated with the occurrence of total organic carbon. Considering that members of the communities consume the analyzed fish, an interdisciplinary approach, including isotopic analysis, methylmercury sampling in humans, and mercury monitoring over time, is imperative for a detailed risk assessment of mercury exposure in Amazonian communities.