Hg Concentrations In Muscle Research Articles

Changes in Carbon, Nitrogen, and Oxygen Stable Isotope Ratios and Mercury Concentrations in Killer Whales (Orcinus orca) during and after Lactation

The changes in the stable isotope ratios of carbon (δ13C), nitrogen (δ15N), oxygen (δ18O), and mercury (Hg) concentrations in muscle and liver tissues during and after lactation were studied in killer whales stranded along the coast of Hokkaido, in the northern area of Japan (n = 16). Calf muscles displayed δ13C- and δ15N-enriched peaks and a δ18O-depleted peak during lactation. The δ13C- and δ15N-enriched peaks appear to reflect the extensive nursing of 13C- and 15N-enriched milk and the onset of weaning, whereas the δ18O-depleted peak may be attributable to the extensive nursing of 18O-depleted milk and the onset of weaning. The δ13C and δ15N values tended to gradually increase after the weaning, whereas the δ18O values tended to decrease. The δ13C and δ15N levels in calves were similar between liver and muscle samples, whereas those in mature animals were higher in liver than in muscle samples. The isotopic turnover rates of C and N may be similar between the liver and muscle tissues in calves, which are rapidly growing animals. The Hg concentrations in muscle tissues were slightly higher in small calves than in large calves, probably due to the Hg transfer across placenta. The Hg concentrations in liver and muscle samples increased with increasing body length, and those in two liver samples from mature animals exceeded the high-risk threshold for marine mammal health effects (82 μg/wet g).

Mercury bioaccumulation and its relationship with trophic biomarkers in a Mediterranean elasmobranch mesopredator

Human activity has led to increased concentrations of mercury (Hg) in the world's oceans. Mercury can bioaccumulate and biomagnify in animal tissues via trophic transfer, thus, becoming most pronounced in larger and older predators. Here, we measured Hg concentrations and their relationship with stable isotopes-based proxies of trophic level (δ13C and δ15N values) in multiple tissues of Mustelus spp. from the Mediterranean Sea. We found higher Hg concentrations in muscle than in liver and fin tissues. The relationship between Hg concentrations and δ15N values in muscle suggested repeated foraging for low trophic level and Hg-poor prey, and biomagnification of Hg at higher trophic levels. Seasonal variations in δ13C values could indicate shifts in primary production sources and/or in local prey availability. The HBVSe index suggested no risk to human health, however the safe meal limit recommendations are 4.5 and 2.2 portions per month for adults and children, respectively.

Compound-specific stable isotopes of amino acids reveal influences of trophic level and primary production sources on mercury concentrations in fishes from the Aleutian Islands, Alaska

Total mercury concentrations ([THg]) exceed thresholds of concern in some Steller sea lion (Eumetopias jubatus) tissues from certain portions of the Aleutian Islands, Alaska. We applied compound-specific stable isotope analyses of both carbon and nitrogen in amino acids from fish muscle tissue to quantify the proportional contributions of primary production sources and trophic positions of eight prey species (n = 474 total) that are part of Steller sea lion diets. Previous THg analyses of fish muscle, coupled with monomethylmercury analyses of a subset of samples, substantiated previous findings that fishes from the west of Amchitka Pass, a discrete oceanographic boundary of the Aleutian Archipelago, have higher muscle Hg concentrations relative to fishes from the east. The δ13C values of essential amino acids (EAAs) in fish muscle demonstrated that although most fishes obtained their EAAs primarily from algae, some species varied in the extent to which they relied on this EAA source. The δ15N values of phenylalanine (0.9 to 7.8 ‰), an indicator of the isotopic baseline of a food web, varied widely within and among fish species. Trophic position estimates, accounting for this baseline variation, were higher from the west relative to the east of the pass for some fish species. Trophic magnification slopes using baseline-corrected trophic position estimates indicated similar rates of Hg biomagnification to the east and west of Amchitka Pass. Multiple linear regression models revealed that trophic position was the most important driver of fish muscle [THg] with less variation explained by other parameters. Thus, higher trophic positions but not the rate of Hg biomagnification to the west of Amchitka Pass may play a role in the regional differences in both fish and Steller sea lion [THg]. Although, differences in Hg contamination and uptake at the base of the east and west food webs could not be excluded.

Integrating Mercury Concentrations in American Alligators (Alligator mississippiensis) with Hunter Consumption Surveys to Estimate Exposure Risk.

Mercury is a naturally occurring element but is also considered a widespread contaminant due to global anthropogenic activity. Even in moderate amounts, mercury (Hg) is an established neurotoxin and is associated with a range of adverse outcomes both in humans and wildlife. Humans in the United States are most commonly exposed to Hg through contaminated food or drinking water, and the consumption of game species, particularly those occupying higher trophic levels, has the potential to expose hunters to high concentrations of Hg. In the present study, we determined Hg concentrations in tail muscle and blood from American alligators (Alligator mississippiensis) inhabiting a region (Savannah River Site, SC, USA) with known Hg contamination. We then integrated these data with alligator harvest records and previously published surveys of alligator meat consumption patterns to estimate potential exposure risk. We found that the average Hg concentrations in tail muscle (1.34 mg/kg, wet wt) from sampled alligators exceeded the recommended threshold for Hg exposure based on the World Health Organization's guidelines (0.5 mg/kg, wet wt). In addition, based on regional consumption patterns reported for both adults and children, we estimated Hg exposures ( = 0.419 µg/kg/day, = 2.24 µg/kg/day) occurring well above the US Environmental Protection Agency methylmercury reference dose of 0.1 μg/kg/day. Although the two reservoirs sampled in the present study are not currently open to alligator hunting, they are connected to waters that are publicly accessible, and the extent of alligator mobility across these sites is not known. Together, the findings reported in the present study further demonstrate the need for active monitoring of Hg concentrations in game species, which can convey substantial exposure risks to the public. Environ Toxicol Chem 2023;42:525-534. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Mercury in fish tissues from the Galapagos marine reserve: Toxic risk and health implications

Fishing is one of the most important economic and cultural activities in Galapagos and Hg presence in aquatic ecosystems is a serious problem for human health, so its concentrations should be studied. We sampled five demersal species (Caulolatilus princeps, Caulolatilus affinis, Mycteroperca olfax, Hyporthodus mystacinus and Pontinus clemensi) and four pelagic species (Coryphaena hippurus, Acanthocybium solandri, Thunnus albacares and Seriolella violacea) to evaluate Hg concentration in muscle, liver and gonads. Hg was analyzed by Cold Vapor Atomic Absorption Spectrophotometry with Flow Injection System (CV-AAS-FIAS). Demersal species had higher Estimated Weekly Intakes (EWI) of Hg than pelagic species. According to the Codex Alimentarius (1995), EFSA (2018), FDA (2021) regulations, and according to the regulations in Europe, A. solandri, P. clemensi, and H. mystacinus were found above the maximum allowed concentration (MAC) (0.65, 0.65 and 1.26 mg/kg wet weight, respectively) so they could not be ingested nor commercialized. The Margin of Safety (MoS) of these species was above 1, so they could pose a risk to human health. We hypothesize that the Hg concentrations found in the studied species could come from the volcanism of the archipelago, since no major sources of anthropogenic Hg contamination can be found in the islands.

Bioaccumulation of Mercury and Radiocesium in Waterfowl Introduced to a Site with Legacy Contamination.

Despite the propensity of waterfowl species to readily accumulate anthropogenic contaminants within polluted environments, few studies have examined bioaccumulation rates over time when entering such a contaminated site. We examined mercury (Hg) and radiocesium (137 Cs) bioaccumulation over time in two waterfowl species released into a wetland system containing legacy contamination on the US Department of Energy's Savannah River Site in South Carolina. Released birds were collected at select time intervals over an exposure period of 94 days. We quantified total Hg concentrations in blood, muscle, and liver tissues, and 137 Cs activity in whole-body and muscle tissues. The relationship between the contaminant burdens of different body tissue types was examined over time. Likely a result of microhabitat selection, mallards in our study readily accumulated both Hg and 137 Cs at consistent rates over time within our study system, while ring-neck ducks did not. The findings demonstrated that whole blood can be used as a robust, nondestructive sampling alternative to estimate Hg burdens within muscle and liver, and whole-body 137 Cs activity is a good predictor of muscle burdens. Understanding such bioaccumulation information in waterfowl is useful for the assessment of the potential health risk in wildlife, as well as being important for human risk assessment toward the consumption of popular game species. Environ Toxicol Chem 2022;41:2479-2487. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Toxicological risk of mercury for fish and invertebrate prey in the Arctic.

We assessed the risks of mercury (Hg) to Arctic marine and freshwater fish by compiling published muscle Hg concentrations and information on tissue concentrations associated with adverse effects. The assessment included 333 groups of fish representing 35 genera and 14,002 individuals sampled from sites across the circumpolar Arctic. Mean or median Hg concentrations in fish muscle varied widely from 0.005 μg/g ww to a maximum of 2.2 μg/g ww. Results indicate that most (n = 139 of 333 or ~ 42%) Arctic fish are not at risk for Hg toxicity, based on the large number of fish mean or median muscle Hg concentrations below 0.1 μg/g ww. A smaller number of the identified groups (n = 76 of 333 or ~ 23%) of Arctic fish had mean or median Hg concentrations consistent with moderate (0.3-0.5 μg/g ww), high (0.5-2 μg/g ww), and severe risk (≥2 μg/g ww). Most of the fish with Hg concentrations in these risk categories were long-lived predators (e.g., non-anadromous Arctic char, northern pike, lake trout, Greenland halibut, Greenland shark). We also, for the first time, conducted a risk assessment of Arctic marine and freshwater invertebrates to evaluate the potential for Hg effects at lower trophic levels and to support risk assessment for Arctic fish. The vast majority (90%) of site-specific Hg or methylmercury (MeHg) concentrations in taxa of marine and freshwater invertebrates (n = 321) were < 0.5 μg/g dw, which is well below critical body residues of Hg in aquatic invertebrates associated with acute and sublethal effects determined in laboratory dosing studies. As the screening-level approach we carried out in the present study is not indicative of actual effects, more studies which directly evaluate the effects of Hg exposure in Arctic fish species are needed. The information here will be of use to Article 22 (Effectiveness Evaluation) of the Minamata Convention.

A Global Review of Cadmium, Mercury, and Selenium in Sharks: Geographical Patterns, Baseline Levels and Human Health Implications

Globally, there is concern about the concentrations of some metals and metalloids in sharks and the associated impacts to themselves and to human consumers. Concentrations of Hg, Cd, and Se reported in muscle, liver and fins of sharks from all the world were reviewed to define geographical patterns of elemental distribution, to model the baseline concentrations of the three elements, and to assess potential human health risk. Published information corresponded to 102 sites that belong to thirteen FAO Major Fishing Areas. The majority of the sites corresponded to the Atlantic (39 sites), followed by the Pacific Ocean (37). Statistical analysis indicated significant differences of elemental concentrations among all FAO regions and oceans. The 5% baseline levels, estimated with a cumulative frequency distribution method for each element were: for Hg, 0.129 μg g−1 in muscle, 0.147 μg g−1 in liver; for Cd, 0.517 μg g−1 in muscle, 0.290 μg g−1 in liver; for Se, 0.105 μg g−1 in muscle, 0.218 μg g−1 in liver. These baseline leves are equivalent to the 5th percentile on a normal distribution. Levels of Cd, Hg and Se in muscle of sharks were above maximum permissible limits (Cd, 0.5; Hg, 1.0; Se, 1.0 μg g−1; Nauen in FAO Fish Circ 764:1–102, 1983; CEC in Off J Eur Union 364:5–24, 2006) for human consumption in 6, 49 and 25% of the reports, respectively. Considering all the studies, hazard quotients (it indicates the risk during the lifetime of an individual different to cancer if value is above one) were Cd (0.10 ± 0.18), Se (0.11 ± 0.10) and Hg (2.05 ± 2.69); i.e. only average Hg values are of concern. The concentrations of Hg and Se in muscle of sharks from the Mediterranean were statistically different from all other oceans. In shark species with more reports, baseline levels (µg g−1 wet weight) of Hg in muscle were: for P. glauca from the Pacific Southeast (0.048), for I. oxyrinchus from the Pacific Southeast (0.034), and for S. lewini from the Pacific Eastern Central (0.55). The balance of Hg and Se molar concentrations (it is used to assess the benefit or risk to the combined occurrence of Hg and Se) in muscle of sharks was assessed through the Se health benefit value (HBVSe), positive results indicate that shark consumption is beneficial to humans. In general, HBVSe was positive (3.06 ± 13.84). According to FAO Fishing areas, negative HBVSe values corresponded to Mediterranean and Black Sea (− 48.37), Atlantic Northwest (− 5.54), Pacific Eastern Central (− 0.97), and Atlantic Southwest (− 0.21); nevertheless, HBVSe values in sharks from Mediterranean and Black Sea, and Atlantic Northwest corresponded to only one species. Overall, similar elemental concentrations were found in some FAO regions of the southern hemisphere. Baseline values of Hg were in the same magnitude order as the low atmospheric deposition flux. Under the approach of the hazard quotient, Hg is of concern because values were above one in almost half of the studies. More information related to Hg and Se in muscle of sharks is required in some FAO regions (Indian Ocean Eastern, Pacific Northeast and Pacific Southeast) to estimate HBVSe.

Pan-oceanic distribution of mercury (Hg) in sea turtles: a review

With no known biological function, mercury (Hg) is highly toxic, bio-accumulates, and biomagnifies up the food web. Long-living marine animals, such as sea turtles, can be exposed to Hg in the oceans. The wide distributions of these reptiles and lifespans compatible with Hg residence time in ocean surface waters (approximately 30 yr) makes them reliable biological monitors of the long-term changes in Hg concentrations in the oceans. Taking this into consideration, we conducted a thorough review of studies to compare the concentrations of Hg in the 7 species of sea turtles distributed in different regions of the Atlantic, Pacific, and Indian Oceans and the Mediterranean Sea. Hg concentrations in muscle and scutes of Chelonia mydas were highest in the South Atlantic, whereas the highest concentrations found in Caretta caretta occurred in the Mediterranean Sea. The differences could be associated with the feeding habits of each species and the characteristics of the environment, such as the oligotrophic nature of the water and the lower productivity in the Mediterranean Sea. Unfortunately, few studies exist for the other 5 sea turtles (Dermochelys coriacea, Eretmochelys imbricata, Lepidochelys olivacea, L. kempii, and Natator depressus), which hampers a more detailed regional or ecological comparison among species. The results found in this review reveal information gaps that should be filled through more numerous studies focused on different oceanic regions and species.

Heavy metals in sediment and fish from two coastal lagoons of the Mexican Central Pacific

The present work analyzed the concentration of As, Cd, Pb, and Hg in sediment and the Hg concentration in fish muscle from two coastal lagoons in the states of Jalisco (Barra de Navidad Lagoon) and Colima (Cuyutlan Lagoon), Mexico. Both lagoons showed relatively low levels of metal contamination and potential health risk compared to other Mexican areas. A non-carcinogenic hazard quotient (HQ) was determined. As (10.7 ± 1.3 - 25.4 ± 3.1 μg g -1 ) and Pb (42.7 ± 4.2 - 123.9 ± 14.7 μg g -1 ) concentrations exceeded the permissible levels, otherwise for Hg and Cd were below the limits. The highest total mercury concentration was found in Haemulopsis sp. and Lutjanus sp. with 0.23 and 0.1 μg g -1 (wet weight) respectively, out of 14 species of fish analyzed that are frequently consumed locally. HQ based on the national daily per capita consumption of fish in Mexico and the consumption of fish associated with fishing communities in Mexico showed an HQs >2, which manifests the vulnerability of these communities to persistent toxic and bioaccumulative contaminants.

Age-specific accumulation of toxic metal(loid)s in northern pike (Esox lucius) juveniles.

Northern pike specimens of 0+, 1+, and 2+ age classes were collected in June 2013 from the Vizelj channel near Belgrade (Serbia). Inductively coupled plasma optical spectrometry (ICP-OES) and atomic absorption spectrometer SpectrAA 220 were used for analyzing concentrations of As, Cr, Cd, Co, Cu, Fe, Sr, Pb, and Zn, as well as Hg in muscle, gills, and liver. Metal pollution index (MPI) was calculated. Concentrations of As, Cd, Co, and Pb were below the limit of detection. Concentrations of Cu, Hg, and Zn in muscle did not exceed the maximum allowed concentrations. The gills were tissue which was most affected by pollution. The highest concentrations of Fe in muscle, Cr and Fe in gills, and Hg, Sr, and Zn in liver were recorded in 0+ individuals, as well as Zn in gills of 2+ individuals. On contrary, the lowest concentrations were recorded for Zn in gills of 0+ individuals, Hg in gills of 1+ individuals, and Fe in muscle, Cr and Sr in gills, and Zn in liver of 2+ individuals. Regarding age classes, 2+ juveniles had the highest MPI values for all tissues. Correlations between the metal(loid) accumulation and fish condition were not significant, as well as between fish length and weight and Cu and Hg in muscle, Cu, Hg, and Sr in gills, and Cu, Cr, and Fe in liver. Results indicated that young individuals were more sensitive to pollution, but older fish showed higher overall bioaccumulation of toxic elements analyzed in this study.

Mercury offloading in gametes and potential adverse effects of high mercury concentrations in blood and tissues of Atlantic Goliath Grouper Epinephelus itajara in the southeastern United States.

Mercury (Hg) is a ubiquitous and non-essential heavy metal that is highly toxic to aquatic organisms. Few studies examine Hg and its effects on wild fish populations. Here, we investigated the potential effects of Hg exposure on a large and long-lived marine species of conservation concern, the vulnerable Atlantic Goliath Grouper Epinephelus itajara. Our objectives were (1) to measure Hg (methyl-Hg; and total Hg=combined methyl-Hg and inorganic-Hg) concentrations in whole blood (WB) and gametes (eggs and sperm); (2) to investigate the relationships between Hg concentrations in muscle and liver with WB and gametes; (3) to investigate the relationships between Hg concentrations in liver, muscle, and WB with hematological and plasma biochemical analytes; and (4) to investigate the relationship between liver Hg and pigmented macrophage aggregates in liver tissue sections. We found several lines of evidence for potential adverse effects on Goliath Grouper health and reproduction by high Hg concentrations in liver, muscle, WB, and gametes, including (1) Hg concentrations in all tissues and gametes were well above observable ranges of marine and freshwater fishes from experimental exposure studies; (2) gamete Hg concentrations were among the highest recorded in wild fishes, with seasonal patterns suggesting females offload significant amounts of Hg into their eggs during the spawning season; (3) Methyl-Hg was highest in muscle, followed by sperm, liver, eggs, and WB; (4) there were significant correlations between liver, muscle, and WB Hg concentrations with various blood analytes; (5) vitellogenin positively correlated with female liver methyl-Hg concentrations, and was abnormally high in males, suggesting direct endocrine effects; and (6) liver total Hg positively correlated with pigmented macrophage aggregate count and percent area. This work will help guide future research examining the potential adverse effects of Hg and its role as an additional stressor on wild fish populations.

Distribution of mercury species in different tissues and trophic levels of commonly consumed fish species from the south Bay of Biscay (France)

Mercury (Hg) is a contaminant of global concern in marine ecosystems, notably due to its ability to accumulate and concentrate in food webs. Concentrations of total mercury (THg), methylmercury (MeHg) and inorganic mercury (IHg) were assessed and compared in different tissues (liver, muscle, and gonads) of three common fish species (hake Merluccius merluccius, red mullet Mullus surmuletus, and sole Solea solea) from the continental shelf from the southern part of the Bay of Biscay. Several studies investigated Hg concentration in fish muscle, but few assessed concentrations in other organs, despite the importance of such data to understand contaminant organotropism and metabolization. Results showed that trophic position and feeding habitat are required to understand the variability of Hg concentration in muscle between fish species. In addition, high MeHg/THg ratio in muscle could be explained by the predatory behavior of the studied fish species and the biomagnification of this Hg species within the food web, MeHg. Despite differences between species, Hg concentration was always higher in muscle (from 118 ± 64 to 338 ± 101 ng g−1 w.w.) and liver (from 122 ± 108 to 271 ± 95 ng g−1 w.w.). These results can be related to physiological processes especially the MeHg detoxification strategies.

Influence of Species-Specific Feeding Ecology on Mercury Concentrations in Seabirds Breeding on the Chatham Islands, New Zealand.

Mercury (Hg) is a toxic metal that accumulates in organisms and biomagnifies along food webs; hence, long-lived predators such as seabirds are at risk as a result of high Hg bioaccumulation. Seabirds have been widely used to monitor the contamination of marine ecosystems. In the present study, we investigated Hg concentrations in blood, muscle, and feathers of 7 procellariform seabirds breeding on the Chatham Islands, New Zealand. Using bulk and compound-specific stable isotope ratios of carbon and nitrogen as a proxy of trophic position and distribution, we also tested whether Hg contamination is related to the species-specific feeding ecology. Mercury exposure varied widely within the seabird community. The highest contaminated species, the Magenta petrel, had approximately 29 times more Hg in its blood than the broad-billed prion, and approximately 35 times more Hg in its feathers than the grey-backed storm petrel. Variations of Hg concentrations in blood and feathers were significantly and positively linked to feeding habitats and trophic position, highlighting the occurrence of efficient Hg biomagnification processes along the food web. Species and feeding habitats were the 2 main drivers of Hg exposure within the seabird community. The Pterodroma species had high blood and feather Hg concentrations, which can be caused by their specific physiology and/or because of their foraging behavior during the interbreeding period (i.e., from the Tasman Sea to the Humboldt Current system). These 2 threatened species are at risk of suffering detrimental effects from Hg contamination and further studies are required to investigate potential negative impacts, especially on their reproduction capability. Environ Toxicol Chem 2021;40:454-472. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Mercury screening in highly consumed sharpnose sharks (Rhizoprionodon lalandii and R. porosus) caught artisanally in southeastern Brazil

Sharpnose sharks Rhizoprionodon lalandii and R. porosus are frequently captured in fishing activities in Brazil and are significantly consumed by humans, especially in southeastern Brazil. Both species lack population data and suffer intense fishing pressures and habitat degradation, consequently hindering adequate management and conservation actions. In this context, this study aimed to assess mercury (Hg) contamination in R. lalandii, and R. porosus sampled off the coast of Rio de Janeiro, addressing both animal health and public health risks. Sharks were obtained from two artisanal fishing colonies in southeastern Brazil (Copacabana and Recreio dos Bandeirantes), located on the coastal zone adjacent to Guanabara Bay, one of the most important, productive, and contaminated estuaries in Brazil, and a further three artisanal fishing colonies from the Região dos Lagos area (Saquarema, Cabo Frio and Rio das Ostras). Hg concentrations in liver, muscle, and brain in R. lalandii (n = 24) and R. porosus (n = 20) specimens were determined by inductively coupled plasma mass spectrometry. A gravid female measuring 112 cm from Copacabana is the first record for an individual of this size for R. lalandii. No correlation between length and muscle Hg concentrations was observed, and no differences between Hg concentrations for muscle or liver were found between male and female juveniles from either Cabo Frio or Rio das Ostras. No differences in Hg loads were observed herein for both assessed species. Low Hg bioaccumulation in juveniles and nongravid female muscle tissue was noted compared to significantly higher Hg concentrations in gravid females. Hg was detected in all embryos, indicating potential maternal offloading. As Hg thresholds for sharks in particular have not yet been established, whether the Hg concentrations detected in brain pose neurotoxic risks for these animals is not known. Public health concerns concerning adult R. lalandii consumption from Copacabana, however, are significant.

No relationship between gastrointestinal parasite intensities or mercury burdens on fluctuating asymmetry in Common Eider (&lt;i&gt;Somateria mollissima&lt;/i&gt;) mandibles

Mercury (Hg) emissions have increased since 1950 and biomagnification in Arctic ecosystems can affect animals, particularly at higher trophic levels. Exposure to Hg can negatively affect young developing animals, resulting in altered morphology and ultimately, lower fitness. We examined the relationship of mandible fluctuating asymmetry (FA) with gastrointestinal helminth intensity and breast muscle Hg concentration in Common Eider (Somateria mollissima borealis). Procrustes analysis of variance indicated significant FA but relatively high measurement error. Based on multiple linear regression modelling, there was no significant relationship between FA and Hg concentration or parasite burden. There may be a mismatch in trying to relate amount of Hg and parasite intensity in adults to FA that would have occurred early in life during skeletal development.

Mercury concentrations in the tissues of blue shark (Prionace glauca) from Sagami Bay and cephalopods from East China Sea

The toxicity of mercury (Hg), is generally known, and around 90% of Hg exist as methylmercury (CH3Hg+) in marine organism. Mercury concentrates in sharks and whales, which are at the top of the food chain as predators to cephalopods. The concentrations of Hg in liver and muscle of blue shark, caught in Sagami Bay, and in digestive gland and mantles of Todarodes pacificus, Sepia madokai, and Uroteuthis edulis caught in East China Sea were measured and analyzed. The Hg concentrations in the sharks, squids, and cuttlefishes determined in this study were almost same as those in the other sea regions. In addition, the Hg concentration in the blue shark was higher in the muscle than in the liver. In S. madokai and U. edulis, Hg accumulated in the digestive gland but not in the mantle. Although the Hg concentration in the digestive gland of T. pacificus is lower than those of S. madkai and U edulis, Hg concentration in the mantle is critically higher. More than 90% of Hg is present as CH3Hg+ in muscle of blue shark and mantle of T. pacificus. This feature is explained due to amino acids with the thiol groups and chain genes in the muscle of blue shark as well as in the mantle of T. pacificus. Myosin in the mantle of T. pacificus and blue shark enhances the stability of CH3Hg+. The amount of Hg in the digestive gland of T. pacificus could be too large to store; thus, Hg is released to the mantle, whereas the nutrients in the digestive gland of T. pacificus are supplied to other tissues. It is considered that the muscle fiber of T. pacificus is strong; therefore, large amounts of myosin levels may be present in T. pacificus than in S. madokai and U. edulis.

Main drivers of mercury levels in Southern Ocean lantern fish Myctophidae

Myctophids are the most abundant fish group in the Southern Ocean pelagic ecosystem and are an important link in the Antarctic marine food web. Due to their major ecological role, evaluating the level of mercury (Hg) contamination in myctophids is important as a step towards understanding the trophic pathway of this contaminant. The concentrations of total Hg were determined in muscle, gill, heart and liver tissue of 9 myctophid species to quantify tissue partitioning variability between species. Organic Hg concentration and proportion in muscle was also determined. Hg concentrations were higher in the liver and heart than in muscle and gills, but the proportion of organic Hg was almost 100% in muscle, indicating that the main uptake route for Hg is through the diet. Most of the species analysed have similar vertical and horizontal distributions, and similar feeding modes and prey. Geographical and temporal variability of Hg concentrations was examined using samples from 3 different sampling cruise (2007/08, 2015/16 and 2016/17) and 2 locations (South Georgia and South Orkneys Islands). Our results appear to indicate a decreasing trend in Hg contamination over the last decade, particularly gill tissue, which is in agreement with a previous study on squid from the same region. There was no significant variability in Hg concentration between the different sampling locations. Hg levels were consistent with values reported previously for myctophids around the world, indicating low global-scale geographic variability. A positive relationship between fish size and Hg concentration was found for most species, with the exception of Electrona antarctica females, which may be explained through Hg elimination by egg laying. We estimate that myctophids collectively comprise a Southern Ocean mercury ‘reserve’ of ≈1.82 metric tonnes.

Hg and Se in Organs of Three Cetacean Species from the Murcia Coastline (Mediterranean Sea).

We determinated Hg and Se concentrations in liver, kidney, brain, lung and muscle of five bottlenose dolphin (Tursiops truncatus), four common dolphins (Delphinus delphis) and four Risso's dolphin (Grampus griseus) stranded along the Murcia coast, Southeast Spain, in order to evaluate the risk of Hg toxicity. Hg concentrations showed similar concentrations to other individuals in the Mediterranean Sea with the same length in the same period. We observed a positive correlation of Hg and Se in liver (r = 0.948, p < 0.001) and kidney (r = 0.939; p = 0.001) and ratio the Se/Hg molar was higher than 1 in most cases. Our results suggest that the protective effects of Se against Hg toxicity occur in cetaceans. However, we detected levels of Hg described as responsible liver damage and neurotoxicological effects so other tools, as biochemical markers, should be included. Besides, more studies are needed to evaluate the risk of Hg exposure in dolphins from Murcia coastline.

Tissue-based assessment of hazard posed by mercury and selenium to wild fishes in two shallow Chinese lakes.

Total (all forms of inorganic and organic) concentrations of mercury (Hg) and selenium (Se) were measured in dorsal muscle and eggs of wild fishes from two shallow lakes in China: Tai Lake (Ch: Taihu; TL) and Baiyangdian Lake (BYDL). Hazard quotients (HQs) were calculated by dividing concentrations of Se or Hg in muscle or eggs of fishes by threshold concentrations for effects expressed as tissue residue toxicity reference values (TR-TRVs). Concentrations of Hg in whole bodies of fishes were estimated by concentrations in muscle. Based on concentrations of Hg in whole body, HQs for fishes in TL and BYDL were less than 1.0, which suggests little to moderate potential for effects on these fishes and unaccepted adverse effects of Hg are unexpected for adult fishes. HQs of Se in muscle of common carp from TL were closed to 1.0, and 27% of HQs based on concentrations of Hg in eggs of fishes from BYDL exceeded 1.0. Potential hazard due to Hg on common carp in TL and reproductive effects of Se on fishes from BYDL exhibited need for concern. Ratios of molar concentrations of Se to Hg were greater than 1.0. Thus, there might be some protective effects of Se on effects of Hg on fishes in TL and BYDL.