Research Progress of Mercury Bioaccumulation in the Aquatic Food Chain, China: A Review

Adaptability of Chub mackerel (Scomber japonicus) under El Niño and La Niña conditions: Body condition, feeding, and contaminant analysis

This study analyzes the effects of the El Niño and La Niña phenomena on the physiological ecology and mercury contamination levels of Chub mackerel, using samples collected from the Northwest Pacific region in 2021 (a La Niña year) and 2023 (an El Niño year). We analyzed body condition (Fulton's K index), trophic dynamics (δ13C, δ15N isotopes), and mercury levels in individuals across size classes (100-300 mm). The results indicate that, smaller mackerel (100-200 mm) exhibited significantly higher K values during El Niño (p < 0.05), whereas larger conspecifics (>250 mm) showed reduced condition. Sexual dimorphism in K (females > males) observed in 2021 disappeared under El Niño, suggesting climate-mediated shifts in energy allocation. Trophic niche breadth expanded during El Niño (6.88 vs. 4.12 SEAc), reflecting dietary diversification toward lower-trophic prey, as evidenced by depleted δ13C and δ15N values. Mercury concentrations surged in 2023, particularly in medium-to-large fish (151-300 mm, p < 0.01). This pattern likely reflects climate-driven intensification of mercury production under colder, oxygen-depleted conditions combined with trophic shifts toward larger, higher-trophic prey that biomagnify mercury more efficiently, collectively indicating that ENSO variability modulates both pollution bioavailability and contaminant transfer dynamics in pelagic food webs. These findings underscore the dual threats of climate-driven ecological disruption and pollution amplification in pelagic ecosystems. By elucidating size- and sex-specific vulnerabilities, this work provides actionable insights for adaptive fisheries management and highlights the urgent need to integrate climate and contaminant monitoring in marine conservation strategies.

Mercury Trophic Transfer and Biomagnification in Food Webs within a Tropical Embayment as Evidenced by Nitrogen and Carbon Stable Isotope Analysis

Mercury (Hg) contamination in marine ecosystems poses a significant environmental threat due to its high toxicity, persistence in the environment, and tendency to bioaccumulate in organisms and biomagnify in food webs. Understanding how Hg moves through these food webs is essential for assessing its ecological and health impacts. To investigate the trophic dynamics of Hg in Rayong Bay, Gulf of Thailand, we collected marine organisms from the pelagic and benthic food webs during 2022-2023 and analyzed the total mercury content (THg) in plankton (phytoplankton, zooplankton, and fish larvae) and in 81 marine animal species. Furthermore, the stable nitrogen and carbon isotope values (δ15N and δ13C) were measured to establish their trophic levels (TLs) and potential food sources in the food web. Based on these analyses, we calculated the biomagnification factor using TL-adjusted ratios (BMFnorm) and trophic magnification factor (TMF) for the different TLs. BMFnorm values exceeded 1.0 in over 40% of cases for both the pelagic and benthic food webs, indicating THg biomagnification from prey to predator. Notably, the pelagic food web exhibited a markedly higher TMF value (TMF = 6.68) compared to that of the benthic food web (TMF = 2.06), suggesting stronger Hg biomagnification within the pelagic food web. Our findings also highlight the consumption risk of Hg in some fish species in the Rayong Bay food webs, emphasizing the need for continued monitoring and mitigation strategies to safeguard both human and ecological health.

Systematic Review and Spatiotemporal Assessment of Mercury Concentration in Fish from the Tapajós River Basin: Implications for Environmental and Human Health

This study reviews the literature on mercury (Hg) pollution in the Tapajós River basin from 1992 to 2022, focusing on the bioaccumulation in fish and the associated health risks to humans via ingesting contaminated species. Variability in Hg bioaccumulation was analyzed from both spatial (sub-basins) and ecological (trophic levels) perspectives. Mercury concentrations in fish muscle tissue and spatial differences in Hg levels were analyzed using nonparametric Kruskal-Wallis ANOVA and mapped with Inverse Distance Weighting. Additionally, a risk assessment of mercury contamination was conducted using the Target Hazard Quotient (THQ) and Maximum Safe Consuming Quantity (MSCQ) indices. Results indicate that Hg contamination is pervasive across the basin, with piscivorous fish showing the highest Hg levels, particularly in the middle Tapajós, upper Tapajs óand Teles Pires sub-basins, identified as contamination hotspots. Piscivorous species exhibited high Target Hazard Quotients (THQ), suggesting health risks for local consumers. The MSCQ values indicated that 75% of the fish species analyzed should be consumed in quantities lower than the current consumption daily average to avoid health risks.

Size-dependent toxic interaction between polystyrene beads and mercury on the mercury accumulation and multixenobiotic resistance (MXR) of brackish water flea Diaphanosoma celebensis

Due to their worldwide distribution and persistence, mercury (Hg), and nano- and microplastics (NMPs) pose major threats to global ocean ecosystems. Hg and NMPs co-exist in the ocean and can interact with each other. However, information on the toxicity of this interaction to marine biota remains limited. Thus, we investigated the toxicological interaction between HgCl2 (Hg) and NMPs by studying the influence of different sizes of polystyrene beads (0.05-, 0.5-, and 6-μm) on Hg accumulation in the brackish water flea Diaphanosoma celebensis. The Hg adsorption capacity of NPs (0.05-μm) was higher than that of MPs (0.5- and 6-μm). Only the group co-exposed to both Hg and NPs showed increased Hg content in D. celebensis. Multixenobiotic resistance (MXR) activity and transcriptional modulation of transporter genes (ABCBs and ABCCs) were decreased by NMP exposure, particularly by NPs, suggesting MXR disruption by NPs. However, only the activity of multidrug resistance-associated proteins (MRPs; ABCCs) increased with Hg exposure and decreased upon NP+Hg co-exposure, indicating an important role of ABCC in Hg efflux. Furthermore, in vivo toxicity tests showed a synergistic toxic interaction between Hg and NPs on the reproduction of D. celebensis. Our findings suggest that NPs have the potential to enhance the toxicity of Hg, increasing Hg accumulation not only by serving Hg as a carrier but also by disrupting MXR.

Impact of source, packaging and presence of food safety management system on heavy metals levels in spices and herbs

Spices and herbs are susceptible to various contaminants, including heavy metals. Our study aimed to quantify the levels of lead (Pb), mercury (Hg), cadmium (As), and cadmium (Cd) in 96 composite samples of 13 herbs and spices frequently consumed in Lebanon. Twenty percent (19/96) and 4% (4/96) of the samples exceeded the permissible levels of Pb and Cd, respectively and all the samples met the permissible levels of As and Hg according to Codex Alimentarius standards. For Pb and Cd, unpackaged samples had the highest levels of unacceptable samples of 31% (8/26) and 8% (2/26), respectively. The samples locally packaged in companies with and without Food Safety Management System (FSMS) had the same levels of unacceptable samples of 12% (3/26) and 4% (1/26) for Pb and Cd, respectively. Imported packaged samples had unacceptable levels of Pb (28% (5/18)) and were acceptable for the three other heavy metals.

Genotoxicity effects in freshwater fish species associated with gold mining activities in tropical aquatic ecosystems

The main aim of this study was to investigate total mercury (THg), methylmercury (MeHg) and arsenic (As) concentrations, and their genotoxic effects on fish species in freshwater habitats impacted by gold mining activities in the Mojana and Bajo Cauca regions (Northern Colombia). A total of 255 individuals of Prochilodus magdalenae (PM) and Hoplias malabaricus (HM) were collected in different areas of northern Colombia, 205 in the exposed groups: Mojana 1 (61), Mojana 2 (81) and Bajo Cauca (63); and 50 individuals in the control group. Dorsal muscle was analysed for pollutants and blood to perform micronucleus (MN) and erythrocytic nuclear alterations (ENA) tests. The results of the MN revealed statistically significant (p < 0.05) genetic damage in both PM (Mojana 1 = 29.7 ± 14.2; Mojana 2 = 25 ± 6.25; Bajo Cauca= 26.6 ± 10.6) and in HM (Mojana 1 = 17.7 ± 7.8; Mojana 2 = 20.4 ± 6.3; Bajo Cauca= 20.8 ± 9.8) compared to the control group (PM= 10.5 ± 3.6; HM= 9.1 ± 3.9). Likewise, the frequency of ENA was statistically higher in the exposed groups compared to the control group (p < 0.05). On the other hand, the concentrations of THg, MeHg and As found in tissue samples were significantly higher (p < 0.05) compared to the control group, being the Bajo Cauca region the area of highest risk due to high concentrations of THg (651.2 ± 344.5 μg/kg for HM and 678.5 ± 983.9 μg/kg for PM) and MeHg (504.6 ± 220.9 μg/kg for HM and 606.8 ± 886.4 μg/kg for PM). Results showed that mean THg values for both species in Bajo Cauca exceeded the WHO maximum limit (set in 500 μg Hg/kg) in fish for human consumption. Results suggest that DNA damage in erythrocytes is associated with the presence of Hg, MeHg and As, coming from mining activities.

Mercury contamination in the riparian ecosystem during the reservoir discharging regulated by a mega dam

Mercury (Hg) is extremely poisonous and can be absorbed through touch, inhalation, or consumption. In the living environment, Hg in contaminated sediment can be transferred into grass by the direct absorption through the roots or shoots. The intake of Hg due to Hg emissions may pose a threat to living bodies especially to human beings. The present study aims to provide a novel insight about total mercury (THg) and methyl mercury (MeHg) in a riparian grass (Cynodon dactylon (L).Pers) and sediments during the discharging phase (summertime at 145 m water level) in Three Gorges Reservoir (TGR-China); where C. dactylon is a dominant perennial herb in the riparian zone. Yet, the potential risk of Hg contamination in the riparian ecosystem is not thoroughly assessed in the dam regulated reservoir. This study was conducted in the riparian zones of the reservoir formed by a mega dam (Three Gorge Dam) which regulates the water levels during the summer and winter period in the TGR. Our results showed that riparian sediments were acting as a sink for THg and MeHg. Insignificant correlation of THg and MeHg was found between the amphiphyte C. dactylon and its surrounding sediments in the TGR. Bioconcentration factors values for MeHg were found higher than 1 in all study locations in the riparian zones in TGR, which could be due to action of certain bacteria/purely chemical-based methylation on inorganic form of Hg. Additionally, translocation factor indices also highlighted that the amphiphyte C. dactylon was MeHg accumulator in riparian zones. These results suggested that since riparian sediment was found acting as the sink for THg and MeHg during discharging phase, MeHg contamination in the amphiphyte C. dactylon in riparian zones was not caused by the riparian sediments but by other factors, for instance, the anthropogenic activities in the TGR. Finally, this study leads to conclude that amphiphyte C. dactylon can be used as biomonitoring agent for Hg pollution in the TGR.

The single and combined effects of mercury and polystyrene plastic beads on antioxidant-related systems in the brackish water flea: toxicological interaction depending on mercury species and plastic bead size

Plastics are considered as a major threat to marine environments owing their high usage, persistence, and negative effects on aquatic organisms. Although they often exist as mixtures in combination with other pollutants (e.g., mercury (Hg)) in aquatic ecosystems, the combined effects of plastics and ambient pollutants remain unclear. Therefore, in the present study, we investigated the toxicological interactions between Hg and plastics using two Hg species (HgCl₂ and MeHgCl) and different-sized polystyrene (PS) beads (diameter: 0.05, 0.5, and 6-μm) in the brackish water flea Diaphanosoma celebensis. The single and combined effects of Hg and PS beads on mortality were investigated, and changes in the antioxidant system and lipid peroxidation were further analyzed. After 48-h exposure to single Hg, HgCl₂ induced a higher mortality rate than MeHgCl. The combined exposure test showed that 0.05-μm PS beads can enhance the toxicity of both the Hg species. The expression of GST-mu, glutathione S-transferease (GST) activity and malondialdehyde (MDA) content increased significantly after exposure to Hg alone (HgCl₂ or MeHgCl) exposure. Combined exposure with PS beads modulated the effects of Hg on the antioxidant system depending on bead size and the Hg species. In particular, the 0.05-μm beads significantly increased the expression level of GST-mu, GST activity and MDA content, regardless of Hg species. These findings suggest that toxicological interactions between Hg and PS beads depend on the type of Hg species and the size of PS beads; nano-sized 0.05-μm PS beads can induce synergistic toxicity with Hg.

Oyster (Crassostrea gigas) ferritin can efficiently reduce the damage of Pb2+in vivo by electrostatic attraction

Heavy metal ions pollution can cause damage to human body through food, so the development of a new kind of macromolecular that can remove heavy metal ions damage has a good application prospect. The possibilities of removing heavy metal ions from food system with ferritin were studied in this paper. In this study, oyster ferritin (GF1) can resistant to denaturation induced by Pb²⁺, Cd²⁺, Cr³⁺ and still maintains its basic structure. GF1 can bind more Pb²⁺, Cd²⁺, Cr³⁺ than recombinant human H-chain ferritin (rHuHF), especially Pb²⁺, and the findings suggest that each GF1 can capture about 51.42 Pb²⁺ in solution. The hard and soft acids and base also verifies that Pb²⁺ have stronger binding ability to the key amino acids at the outer end of the three-fold symmetry channel. Cells preprotected by ferritin could resistant to heavy metal ions. And GF1 can reduce the high blood lead in mice and may play a role in alleviating lead poisoning in vivo. All findings demonstrated that GF1 can be used as a novel macromolecule to bind heavy metal ions, and the study can broaden the research scope of ferritin in contaminated food systems.

Mercury pollution in China: implications on the implementation of the Minamata Convention

Mercury (Hg) is a toxic metal released into the environment through human activities and natural processes. Human activities have profoundly increased the amount of Hg in the atmosphere and altered its global cycling since the Industrial Revolution. Gaseous elemental Hg is the predominant form of Hg in the atmosphere, which can undergo long-range transport and atmospheric deposition into the aquatic systems. Hg deposition elevates the methylmercury (MeHg) level in fish through bioaccumulation and biomagnification, which poses a serious human health risk. Acute poisoning of MeHg can result in Minamata disease, while low-level long-term exposure in pregnant women can reduce the intelligence quotient of infants. After five sessions of intergovernmental negotiation, the Minamata Convention on mercury entered into force in August 2017 to protect human health and the environment from Hg pollution. Currently China contributes the largest quantity of Hg production, consumption, and emission globally. However, the status of Hg pollution in the environment in China and its associated health risk remains relatively unknown, which hinders the development of implementation plans of the Minamata Convention. In this paper, we provide a comprehensive review on the atmospheric release of Hg, distribution of air Hg concentration, human exposure to MeHg and health impacts caused by Hg pollution in China. Ongoing improvement of air pollution control measures is expected to further decrease anthropogenic Hg emissions in China. Air Hg concentrations in China are higher than the background values in the Northern Hemisphere, with spatial distribution largely influenced by anthropogenic emissions. Long-term observations of GEM in China show a decline in recent years. The net Hg transport outflow from China in 2013 is estimated to be 511 t year^-1, and ∼60% of such outflow is caused by natural surface Hg emissions. Hg concentrations in fish and rice in China are relatively low and therefore the associated risks of human Hg exposure are low. Future research needs and recommendations for the implementation of the Minamata Convention are also discussed in this paper.

Characterization of a mercury tolerant strain of Staphylococcus arlettae from Darjeeling hills with an account of its antibiotic resistance pattern and metabolome

Mercury (Hg) is a ubiquitous heavy metal grouped with the top ten most toxic pollutants affecting both human and environmental health. Consequently, mercury contamination due to anthropogenic interference has become a rising global concern. The bacterial strain MTD10A was isolated from soil samples collected over the Darjeeling hills. Heavy metal tolerance study conducted exhibited considerable tolerance to mercury by this bacterial isolate at unprecedented concentrations of up to 0.1 mg/mL of HgCl2. Biochemical characterization and molecular identification via 16S rRNA sequencing identified this highly tolerant bacteria as a strain of a Coagulase Negative Staphylococcus arlettae. This study also maps the resistance pattern of MTD10A against clinically relevant antibiotics and contains a broad assessment of the metabolomic profile of the bacteria achieved via GC-MS. Tolerance of MTD10A to such excessive levels of mercury shown in our study suggests the possibility of a promising candidate for bioremediation in heavily mercury contaminated areas.

Relative contribution of rice and fish consumption to bioaccessibility-corrected health risks for urban residents in eastern China

There are global concerns about dietary exposure to metal(loid)s in foods. However, little is known about the relative contribution of rice versus fish to multiple metal(loid) exposure for the general population, especially in Asia where rice and fish are major food sources. We compared relative contributions of rice and fish consumption to multi-metal(loid) exposure on the city-scale (Nanjing) and province-scale in China. The effects of ingestion rate, metal(loid) level, and bioaccessibility were examined to calculate modeled risk from Cu, Zn, total As (TAs), inorganic As (iAs), Se, Cd, Pb, and methylmercury (MeHg). Metal(loid) levels in rice and fish samples collected from Nanjing City were generally low, except iAs. Metal(loid) bioaccessibilities in fish were higher than those in rice, except Se. Calculated carcinogenic risks induced by iAs intake (indicated by increased lifetime cancer risk, ILCR) were above the acceptable level (1 0 ^-4) in Nanjing City (median: 3 × 10^-4 for female and 4 × 10^-4 for male) and nine provinces (1.4 × 10^-4 to 5.9 × 10^-4) in China. Rice consumption accounted for 85.0% to 99.8% of carcinogenic risk. The non-carcinogenic hazard quotients (HQ) for single metals and hazard index (HI) for multi-metal exposure were < 1 in all cases, indicating of their slight non-carcinogen health effects associated. In Guangdong and Jiangsu provinces, results showed that rice and fish intake contributed similarly to the HI (i.e., 42.6% vs 57.4% in Guangdong and 54.6% vs 45.4% in Jiangsu). Sensitivity analysis indicated that carcinogenic risk was most sensitive to rice ingestion rate and rice iAs levels, while non-carcinogenic hazard (i.e., HQ and HI) was most sensitive to ingestion rate of fish and rice, and Cu concentration in rice. Our results suggest that rice is more important than fish for human dietary metal(loid) exposure risk in China, and carcinogenic risk from iAs exposure in rice requires particular attention.

The silver linings of mercury: Reconsideration of its impacts on living organisms from a multi-timescale perspective

Research on mercury (Hg), a naturally occurring element in Earth's lithosphere, has been extremely hot in the past few decades due to the outbreak of a series of disastrous poisoning incidents. However, such studies might provide us a biased view towards Hg if no thorough review about its long-term effects on living organisms from a multi-timescale perspective was performed. Hg might have played a mysterious role in critical intervals (e.g., mass extinction and oceanic anoxia events) in several geologic periods due to the elevated Hg levels induced by volcanism whereas it has long been used for various purposes in human history. Therefore, it is necessary to go through previous studies and historical records of different timescales (10⁰ to 10⁶ yr). In this work, we conducted a thorough review of Hg knowledge at three different timescales, i.e., geologic periods (10⁶ yr), human history (10³ yr), and contemporary history (10⁰ yr), summarizing recent advances and indicated potential research gaps. By doing so, we demonstrated that it is possible to achieve safe and sustainable Hg applications despite the current Hg crisis. However, such silver linings depend on a better understanding of ecosystem dynamics. Besides, considering the possible dire consequences of erupted Hg levels as suggested in geological periods, swift actions to mitigate the impacts of anthropogenic activities on the Hg cycle will be another key point. Overall, this review presented a unique perspective of Hg combining different timescales, shedding light on the importance of a better understanding of the global ecosystem as a whole and maintaining the sustainability of planet Earth in the future.

Trophic transfer and dietary exposure risk of mercury in aquatic organisms from urbanized coastal ecosystems

In this study, 26 surface seawater samples, 26 surface sediment samples and 114 organisms were collected to study the trophic transfer and dietary exposure risk of mercury (Hg) in organisms from the Jiaozhou Bay, which is a typical semi-enclosed urbanized bay. The total mercury (THg) and methylmercury (MeHg) concentrations did not exceed the threshold limits and performed as: fish > crustaceans > mollusks. The trophic level values (TLs) were less than 3 in all the groups, indicating simple structure of food chain. With the increasing δ¹⁵N value, THg and MeHg were significantly biomagnified in the mollusks and fish but not in the crustaceans. In addition, the bioaccumulation and biomagnification of MeHg were higher than inorganic mercury (IHg) in the aquatic food chain. Target hazard quotient (THQ) and provisional tolerable weekly intake (PTWI) indicated that Hg exposure via consumption of seafood from the Jiaozhou Bay did not pose significant health risks for general population. Consuming fish will face the higher health risk than crustaceans and mollusks, especially in urban regions. Moreover, the risk of MeHg caused by intaking seafood deserved more attention. Trophic transfer function (TTF) explicated the transfer of Hg in the ecosystem and higher trophic transfer efficiency of MeHg than IHg. TTF interpreted the terrestrial input of Hg should be controlled to ensure the safety of consuming seafood from the Jiaozhou Bay.

Concentraciones de metilmercurio en Prochilodus magdalenae (Teleostei: Curimatidae) y Hoplias malabaricus (Teleostei: Erythrinidae) en la cuenca baja del río Cauca-Magdalena, norte de Colombia

Las emisiones de mercurio (Hg) a partir de actividades de minería afectan los recursos pesqueros, los cuales son importantes en la alimentación proteínica de las poblaciones humanas. El objetivo de este estudio fue analizar las concentraciones de MeHg (metilmercurio) en Prochilodus magdalenae (Bocachico) y Hoplias malabaricus (Moncholo) en hábitats continentales de la región de La Mojana y en la parte baja del río Cauca (Norte de Colombia), sitios que han sido afectados por actividades de minería aurífera. Un total de 160 ejemplares fueron colectados para su respectivo análisis, 130 en el grupo expuesto: Mojana 1 (n=36), Mojana 2 (n=56) y El Bajo Cauca (n=38), y n=30 en el grupo control. Se realizaron las determinaciones de MeHg mediante análisis directo con un Analizador Directo de Mercurio DMA 80, cromatografía líquida y espectrometría de absorción atómica. Las concentraciones de MeHg encontradas en muestras de tejido del músculo dorsal de los peces procedentes de los lugares expuestos, fueron significativamente mayores comparados con el grupo control (p< 0.05), siendo la región del Bajo Cauca la más afectada por altas concentraciones de MeHg. Los resultados indican que la presencia de MeHg en los peces es consecuencia de las actividades de minería aurífera ampliamente desarrolladas en la zona. Estas concentraciones MeHg representan un riesgo mortal para la salud humana y animal.

Structural Insights for the Stronger Ability of Shrimp Ferritin to Coordinate with Heavy Metal Ions as Compared to Human H-Chain Ferritin

Although apoferritin has been widely utilized as a new class of natural protein nanovehicles for encapsulation and delivery of nutraceuticals, its ability to remove metal heavy ions has yet to be explored. In this study, for the first time, we demonstrated that the ferritin from kuruma prawns (Marsupenaeus japonicus), named MjF, has a pronouncedly larger ability to resist denaturation induced by Cd²⁺ and Hg²⁺ as compared to its analogue, human H-chain ferritin (HuHF), despite the fact that these two proteins share a high similarity in protein structure. Treatment of HuHF with Cd²⁺ or Hg²⁺ at a metal ion/protein shell ratio of 100/1 resulted in marked protein aggregation, while the MjF solution was kept constantly clear upon treatment with Cd²⁺ and Hg²⁺ at different protein shell/metal ion ratios (50/1, 100/1, 250/1, 500/1, 1000/1, and 2500/1). Structural comparison analyses in conjunction with the newly solved crystal structure of the complex of MjF plus Cd²⁺ or Hg²⁺ revealed that cysteine (Cys) is a major residue responsible for such binding, and that the large difference in the ability to resist denaturation induced by these two heavy metal ions between MjF and HuHF is mainly derived from the different positions of Cys residues in these two proteins; namely, Cys residues in HuHF are located on the outer surface, while Cys residues from MjF are buried within the protein shell. All of these findings raise the high possibility that prawn ferritin, as a food-derived protein, could be developed into a novel bio-template to remove heavy metal ions from contaminated food systems.

Erythrocytes as a Model for Heavy Metal-Related Vascular Dysfunction: The Protective Effect of Dietary Components

Heavy metals are toxic environmental pollutants associated with severe ecological and human health risks. Among them is mercury (Hg), widespread in air, soil, and water, due to its peculiar geo-biochemical cycle. The clinical consequences of Hg exposure include neurotoxicity and nephrotoxicity. Furthermore, increased risk for cardiovascular diseases is also reported due to a direct effect on cardiovascular tissues, including endothelial cells, recently identified as important targets for the harmful action of heavy metals. In this review, we will discuss the rationale for the potential use of erythrocytes as a surrogate model to study Hg-related toxicity on the cardiovascular system. The toxic effects of Hg on erythrocytes have been amply investigated in the last few years. Among the observed alterations, phosphatidylserine exposure has been proposed as an underlying mechanism responsible for Hg-induced increased proatherogenic and prothrombotic activity of these cells. Furthermore, following Hg-exposure, a decrease in NOS activity has also been reported, with consequent lowering of NO bioavailability, thus impairing endothelial function. An additional mechanism that may induce a decrease in NO availability is the generation of an oxidative microenvironment. Finally, considering that chronic Hg exposure mainly occurs through contaminated foods, the protective effect of dietary components is also discussed.

Mercury, microcystins and Omega-3 polyunsaturated fatty acids in farmed fish in eutrophic reservoir: Risk and benefit assessment

Fish is an important source of nutritional omega-3 (n-3) polyunsaturated fatty acids, but it also readily accumulates toxic mercury (Hg) and microcystins (MC) in eutrophic aquatic systems. In China, farmed fish was widely consumed, and aquaculture has caused pervasive eutrophication of freshwater lakes, resulting in the increasing accumulation of MC in fish tissue. To assess the risk-benefit of consuming farmed fish, 205 fish samples of 10 primary species were collected from the eutrophic Wujiangdu (WJD) Reservoir, SW China. The contents of Hg, microcystin-RR (MC-RR), microcystin-LR (MC-LR), and polyunsaturated fatty acids (PUFA) in fish were analyzed. The results showed that THg and MeHg concentrations in all fish sampls were well below the safety limit (500 ng/g w.w) established by the Standardization Administration of China, with average values of 22.9 ± 22.8 and 6.0 ± 6.6 ng/g wet weight (w.w.), respectively. Average concentrations of MC-RR and MC-LR were 40 ± 80 and 50 ± 80 ng/g w.w., respectively. MC-RR and MC-LR concentrations in fish were significantly higher in silver carp and black carp than in perch and catfish (p < 0.05). In nutritional terms, average concentrations of n-3 PUFA and the eicosapentaenoic (EPA) + docosahexaenoic acids (DHA) of fish were 2.0 ± 2.5 and 1.4 ± 0.5 mg/g w.w., respectively. The risk-benefit assessment suggests that the n-3 PUFA benefits from consuming all farmed fish species in the WJD Reservoir outweigh the adverse effects of MeHg. However, except for perch, most fish species still pose a high MC-LR exposure risk that created a requirement for fish consumption advisories and monitoring. Consequently, more attention should be paid on the health risk of combined exposure to pollutants by aquatic product consumption.

16-Mer ferritin-like protein templated gold nanoclusters for bioimaging detection of methylmercury in the brain of living mice

Methylmercury (MeHg⁺) as one of the most potent neurotoxins is mainly accumulated in brain, so in vivo imaging detection of MeHg⁺ in brain is of crucial importance. Herein, we reported a photoluminescent nanosensor for MeHg⁺ detection in brain by integrating the bioimaging of gold nanoclusters (Au NCs), the fluorescence of Au NCs quenched by MeHg⁺, and the brain targeting feature of our recently constructed 16-mer shell-like protein (7A). First, Au NCs with 7A as a biotemplate (7A-Au NCs) by a facile and green method in water are fabricated for the first time, the fluorescence of which (∼650 nm) can be quenched by MeHg⁺ in a dose-dependent manner in vitro. Second, the as-prepared 7A-Au NCs are not only suitable for bioimaging of BBB endothelial cells, but also are an effective probe for bioimaging MeHg⁺ detection in a brain-specific manner. These findings open a door for MeHg⁺ detection in the brain of living subjects.

Methylmercury produced in upper oceans accumulates in deep Mariana Trench fauna

Monomethylmercury (MMHg) is a potent toxin that bioaccumulates and magnifies in marine food webs. Recent studies show abundant methylated Hg in deep oceans (>1000 m), yet its origin remains uncertain. Here we measured Hg isotope compositions in fauna and surface sediments from the Mariana Trench. The trench fauna at 7000-11000 m depth all have substantially positive mass-independent fractionation of odd Hg isotopes (odd-MIF), which can be generated only in the photic zone via MMHg photo-degradation. Given the identical odd-MIF in trench fauna and North Pacific upper ocean (<1000 m) biota MMHg, we suggest that the accumulated Hg in trench fauna originates exclusively from MMHg produced in upper oceans, which penetrates to depth by sorption to sinking particles. Our findings reveal little in-situ MMHg production in deep oceans and imply that anthropogenic Hg released at the Earth's surface is much more pervasive across deep oceans than was previously thought.

Effect of aquaculture on mercury and polyunsaturated fatty acids in fishes from reservoirs in Southwest China

Aquaculture can affect the polyunsaturated fatty acids (PUFA) and mercury (Hg) in fish by altering their diet. Here, planktivorous (silver carp and bighead carp), omnivorous and carnivorous fish with different dietary strategies were selected from two reservoirs, one with on-going aquaculture (WJD) and another without aquaculture (HF) in Southwest China. We compared the total mercury (THg), methylmercury (MeHg) contents and PUFA profiles of fish and their potential diets in these two reservoirs. THg and MeHg contents in omnivorous and carnivorous fish were lower from the WJD Reservoir, which is related to the lower THg and MeHg contents in the artificial fish food. THg and MeHg contents in silver carp from the WJD Reservoir were lower than those from the HF Reservoir, while they were similar in bighead carps from the two reservoirs. The Hg variation in planktivorous fish were inconsistent with that in plankton. THg contents in phyto- and zooplankton from the HF Reservoir were higher than those from the WJD Reservoir, yet their MeHg contents were similar. Artificial fish food which contained higher total PUFA eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), significantly increased the total PUFA and EPA + DHA contents in carnivorous fish, but had less effect on that in omnivorous fish from the WJD Reservoir. Eutrophication caused by aquaculture reduced total PUFA and EPA + DHA contents of plankton in WJD, yet did not reduce those in planktivorous fish. The impacts of aquaculture on Hg and PUFA accumulated in fish were varied among different fish species, and the mechanism needs further exploration.