Total mercury and methylmercury levels in some New Zealand commercial marine fish species

Two groups of samples spanning 16 years are reported for methylmercury and total mercury. All the samples had been taken from commercial catches and represent 33 different commercially important New Zealand marine fish species. Results show the New Zealand fish species sampled have mean contents of total mercury that range between 0.02 and 2.48 mg kg^-1 and mean contents of methylmercury that range from less than 0.04 to 1.97 mg kg^-1.     

Dietary selenium reduces retention of methyl mercury in freshwater fish

Adverse effects from organic mercury transported along aquatic food chains are health issues in humans and other top predators. Methyl mercury in organisms at the lower food chain levels is eliminated slowly, and laboratory studies have not clarified the role of selenium in the retention of methyl mercury in fish. Here, we investigated the effects of dietary selenium on the retention of organic and inorganic mercury in freshwater fish. Addition of selenite to the food augmented elimination of methyl mercury (but not inorganic mercury) from goldfish Carassius auratus in a dose dependent manner; selenite caused methyl mercury to be lost from the general body rather than from any specific organ. Seleno-cystine and seleno-methionine (but not selenate) likewise promoted elimination of methyl mercury from goldfish. The threshold for the augmenting effect of selenite on the elimination of methyl mercury in the zebra fish Danio rerio was 0.95 μg Se g(-1) food; higher concentrations reduced retention of methyl mercury in a dose dependent manner. Selenium concentrations in the food approaching natural background levels increase the elimination of methyl mercury from fish. Thus, selenium levels in a given aquatic food chain may affect mercury contamination along the food chain.     

Location of lipid-soluble selenium in marine fish to the lipoproteins

It has been established that a lipid-soluble selenium compound is enriched in high molecular weight (m.w. ≥5000) extracts from fish. The selenium compound is also enriched in oil extracted from fish by a mixture of non-polar and polar organic solvents (hexane-isopropanol) as compared to the oil extracted with non-polar solvents (hexane) only. When raw fish material is stored it gradually deteriorates and the selenium content in oil produced by boiling of the raw fish material, increases with time. The results indicate that at least part of the lipid-soluble selenium is bound as a lipoprotein.     

Methylated mercury species in Canadian high Arctic marine surface waters and snowpacks

We sampled seawater and snowpacks in the Canadian high Arctic for methylated species of mercury (Hg). We discovered that, although seawater sampled under the sea ice had very low concentrations of total Hg (THg, all forms of Hg in a sample; on average 0.14-0.24 ng L(-1)), 30-45% of the THg was in the monomethyl Hg (MMHg) form (on average 0.057-0.095 ng L(-1)), making seawater itself a direct source of MMHg for biomagnification through marine food webs. Seawater under the ice also contained high concentrations of gaseous elemental Hg (GEM; 129 +/- 36 pg L(-1)), suggesting that open water regions such as polynyas and ice leads were a net source of approximately 130 +/- 30 ng Hg m(-2) day(-1) to the atmosphere. We also found 11.1 +/- 4.1 pg L(-1) of dimethyl Hg (DMHg) in seawater and calculated that there could be a significant flux of DMHg to the atmosphere from open water regions. This flux could then resultin MMHg deposition into nearby snowpacks via oxidation of DMHg to MMHg in the atmosphere. In fact, we found high concentrations of MMHg in a few snowpacks near regions of open water. Interestingly, we discovered a significant log-log relationship between Cl- concentrations in snowpacks and concentrations of THg. We hypothesize that as Cl- concentrations in snowpacks increase, inorganic Hg(II) occurs principally as less reducible chloro complexes and, hence, remains in an oxidized state. As a result, snowpacks that receive both marine aerosol deposition of Cl- and deposition of Hg(II) via springtime atmospheric Hg depletion events, for example, may contain significant loads of Hg(II). Overall, though, the median wet/dry loads of Hg in the snowpacks we sampled in the high Arctic (5.2 mg THg ha(-1) and 0.03 mg MMHg ha(-1)) were far below wet-only annual THg loadings throughout southern Canada and most of the U.S. (22-200 mg ha(-1)). Therefore, most Arctic snowpacks contribute     

Total mercury levels in commercial fish species from Italian fishery and aquaculture

ABSTRACT

Total mercury levels were measured in 42 commercial fish species caught off the Central Adriatic and Tyrrhenian coasts of Italy and in 6 aquaculture species. The study on wild fish covered species differing in living habitat and trophic level. The study on farmed fish covered marine and freshwater species from intensive and extensive aquaculture and their feed. Mercury levels were analysed by thermal decomposition–amalgamation–atomic absorption spectrophotometry. Total mercury concentrations in the muscle of wild fish showed a high variability among species (0.025–2.20 mg kg^?1 wet weight). The lowest levels were detected in low trophic-level demersal and pelagic–neritic fish and in young individuals of high trophic-level species. Levels exceeding the European Commission limits were found in large-size specimens of high trophic-level pelagic and demersal species. Fish from intensive farming showed low levels of total mercury (0.008–0.251 mg kg^?1). Fish from extensive rearing showed variable contamination levels, depending on the area of provenience. An estimation of the human intake of mercury associated to the consumption of the studied fish and its comparison with the tolerable weekly intake is provided.     

Total and organic mercury,selenium and α‐tocopherol in some deep‐water fish species

BACKGROUND: Mercury is a well‐known toxic element present in seafood. Nevertheless some antioxidants, like selenium, as an integral component of the enzyme glutathione peroxidase, and α‐tocopherol having a protective role against it, are present as well. The purpose of this study was to evaluate the levels of total mercury (Hg_T), organic mercury (Hg_Org), Se and α‐tocopherol in some adult deep‐water fish species caught off Portuguese waters. RESULTS: Levels of Hg_T were above EU limits in 6% of Lophius spp. and Aphanopus carbo, 2% of Lepidorhombus spp. and 70% of Helicolenus dactylopterus. Hg_Org represented the major fraction (more than 84%) of Hg_T in all studied muscles. The selenium concentration in muscle was similar in all species (about 0.4 mg kg^?1 wet weight) and the highest level of α‐tocopherol (70 mg kg^?1 wet weight) was found in Aphanopus carbo. CONCLUSION: The muscle of all species studied is a good source of selenium, but only can give a small contribution of α‐tocopherol. Attending to the provisional tolerable weekly intake established by the WHO/FAO for methylmercury, it appears that the species studied should be consumed sparingly. Copyright © 2008 Society of Chemical Industry     

Fatty acid composition of eight species of Indian marine fish

Tropical fish oils were found to be relatively saturated. The species examined showed wide variations in myristic acid (2 to 11.3), palmitic (20 to 35) stearic (7 to 16), C_18:1 (7.9 to 24), C_20:5 (1 to 11) and C_22:6 (2 to 10). Mussel lipids and lipids of mullet contained very high percentages of odd numbered fatty acids.     

Relationship between total mercury concentration and fish size in two pelagic fish species: implications for consumer health

Total mercury concentrations were determined in different size classes of two pelagic fish species of great commercial importance, horse mackerel (Trachurus trachurus) and Mediterranean horse mackerel (Trachurus mediterraneus), to evaluate the relationship between total mercury concentration and fish size and to determine whether any differences might affect the quantitative assessment of mercury exposure for consumers. Mercury concentrations in horse mackerel and in Mediterranean horse mackerel were between 0.16 and 2.41 microg g(-1) of weight wet (mean, 0.68 microg g(-1)) and between 0.09 and 1.62 microg g(-1) (mean, 0.51 microg g(-1)), respectively. The regression curves revealed a significant relationship between mercury concentration and fish size (length and weight) for both species. Concentrations exceeding the proposed limit for human consumption were observed in 33.3% of the samples of both species and were associated with larger specimens. The consumption of the larger specimens could lead to an increase in mercury exposure for consumers. Estimated weekly intakes, calculated on the basis of concentrations relative to each size class, revealed a high exposure associated with the consumption of fish larger than 30 cm (horse mackerel, 11.63 to 20.16 microg/kg of body weight; Mediterranean horse mackerel, 5.86 to 13.55 microg/kg of body weight). An understanding of the factors leading to an increase in mercury exposure can help consumers make informed decisions about eating fish.     

Survey of total mercury in some edible fish and shellfish species collected in Canada in 2002

Total mercury was measured in the edible portions of 244 selected fish and shellfish purchased in Canada at the retail level. By species, average mercury concentrations ranged from 0.011 μg g^-1 for oysters to 1.82 μg g^-1 for swordfish. The predatory fish contained the highest concentrations of mercury: swordfish (mean 1.82 μg g^-1, range 0.40-3.85 μg g^-1), marlin (1.43, 0.34-3.19 μg g^-1), shark (1.26, 0.087-2.73 μg g^-1), and canned, fresh and frozen tuna (0.35, 0.020-2.12 μg g^-1). Levels of mercury in the fresh and frozen tuna contained a mean of 0.93 μg g^-1 (range 0.077-2.12 μg g^-1) and were substantially higher than in the canned tuna (0.15, 0.02-0.59 μg g^-1). In the canned tuna, mercury concentrations varied with subspecies, with the highest average concentrations being found in Albacore tuna (mean 0.26 μg g^-1, range 0.19-0.38 μg g^-1) and the lowest (0.047, 0.025-0.069 μg g^-1) in five samples for which the subspecies of tuna were not identified. Mean concentrations of mercury in swordfish and fresh and frozen tuna were up to three times higher than reported for the USA. Dietary intake estimations found that provided fresh and frozen tuna, marlin, swordfish or shark are consumed once a month or less, the dietary intakes of total mercury by women of child-bearing age, averaged over 1 month, would fall below the Joint FAO/WHO Expert Committee on Food Additives provisional tolerable weekly intake for total mercury. The current Canadian advisory to children and women of child-bearing age is to limit their consumption of fresh and frozen tuna, swordfish and shark to no more than one meal per month.     

基于鱼明胶分散体系SeNPs制备及其抗氧化性研究

采用鱼明胶分散体系制备纳米硒颗粒(SeNPs),利用动态光散射法、扫描电镜对其粒径、消化稳定性以及形貌进行表征,并对其体外抗氧化能力进行测定。结果表明:鱼明胶可作为SeNPs制备的良好分散体系,SeNPs形貌、粒径大小不受鱼明胶分散体系浓度的影响。1.000%,0.500%,0.125%鱼明胶体系制备的SeNPs表现出良好的体外抗氧化能力,其中DPPH自由基清除IC50值分别为1.846 0,0.923 0,<0.461 5 mg/mL;ABTS自由基清除IC50值分别为0.580 0,0.387 1,<0.193 5mg/mL;不同浓度鱼明胶分散体系制备SeNPs还原力依次为0.125%鱼明胶体系>0.500%鱼明胶体系>1.000%鱼明胶体系。SeNPs在胃消化过程中会出现短暂的团聚现象,在肠消化过程中又会重新恢复纳米尺寸。     

Fatty acid composition in some selected marine fish species living in Turkish waters

The muscle fatty acid (FA) composition of 12 selected marine fish species living in Turkish waters was determined. FA profiles of muscle were compared in terms of total and individual saturated (SFAs) and unsaturated fatty acids. Total SFA, monounsaturated fatty acid (MUFA), n‐3 polyunsaturated fatty acid (n‐3 PUFA) and n‐6 polyunsaturated fatty acid (n‐6 PUFA) contents as well as n‐3/n‐6 FA and eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) ratios differed (P < 0.01) in all fish species. Palmitic acid (16:0) among total SFAs, oleic acid (18:1n‐9) among MUFAs, DHA (22:6n‐3) among n‐3 PUFAs and 18:2n‐6 and 20:4n‐6 among n‐6 PUFAs were the most abundant FAs. The ratio of n‐3/n‐6 PUFA contents, indicating the availability of n‐3 PUFAs that are beneficial for human health, ranged from 2.67 to 12.61. The EPA/DHA ratio was between 0.17 and 0.83 in the marine fish species studied. Copyright © 2005 Society of Chemical Industry     

Shelf life of several marine fish species of Bangladesh during ice storage

Organoleptic, biochemical and bacteriological aspects of five tropical marine fish such as silver jewfish, Bombay duck, big-eye tuna, Chinese pomfret and ribbon fish stored in ice were studied. Organoleptically all fish were found acceptable for 10–13 days before becoming inedible. Proximate analysis showed that moisture content increased slightly; protein and lipid content decreased gradually and ash had little or no significant change. pH, TVB-N, peroxide and aerobic plate count values increased with increasing storage period but the values were within acceptable range up to 10 days of storage. Changes in myofibrillar ATPase activity and solubility of these fishes showed that Ca²⁺ ATPase in the presence of both 0.1  m and 0.5  m KCl decreased gradually whereas no marked changes were observed in the Mg⁺² ATPase activities in the presence/absence of Ca⁺². Myofibrillar protein solubility of all fish samples also decreased considerably during ice storage. The decrement in Ca²⁺ ATPase activity and solubility indicates denaturation of myofibrillar protein of fish samples during ice storage.     

Simultaneously determination of methyl and inorganic mercury in fish species by cold vapour generation atomic absorption spectrometry

A simple and rapid non-chromatographic method was developed to determine methylmercury (MeHg) and inorganic mercury (iHg) levels in muscles tissues of 10 freshwater fish species. The MeHg and iHg were determined by cold vapour atomic absorption spectrometry after alkaline wet digestion of samples. The digested samples were reduced sequentially with stannous chloride and sodium tetrahydroborate for iHg and MeHg, respectively. Parameters such as carrier gas flow rate (argon), volume of oxidizing and potassium persulphate solutions were investigated in detail. The accuracy of the technique was evaluated by using certified reference material (DORM-2) and spiking the both Hg species in muscles tissue of a fish. The limits of detection were 0.117 and 0.133 μg kg⁻¹ for MeHg and iHg, respectively. The concentrations of MeHg and iHg in muscles tissues of ten fish species were found in the range of (28.4–56.3) and (3.01–8.11) μg kg⁻¹, respectively.     

Analysis of arsenic and selenium in marine raw materials

The content of arsenic and selenium has been analysed in the following marine organisms: cod (Gadus morhua), herring (Clupea harengus), mackerel (Scomber scomber), Norway haddock (Sebastes marinus), lobster (Homarus vulgaris), mussel (Mytilus edulis), clam (Pecten maximus), oyster (Ostrea edulis), squid (Ommastrephes sagittatus) and whale (Balaenoptera physalus). The analyses were performed both on the raw material and in the water-soluble phase after the samples had been boiled (the N liquor). An enrichment of arsenic is observed in the N liquor, compared with the raw material. The results indicate that selenium is also enriched in the N liquor from fish, but not from the invertebrate animals analysed. The N liquor and the water-soluble phase of the enzyme-hydrolysed presscake (the water-insoluble phase after boiling) were fractionated by molecular gel nitration. Fractions from these elutions were analysed for arsenic and selenium. Selenium was present in the fractions with a molecular weight above about 5000. Arsenic was connected with the lower molecular weight fractions, and may be present as more arseno-organic compounds.     

转基因大豆对硒的富集作用和形态分布研究

目的研究转基因大豆对硒的富集作用以及富集前后转基因大豆中硒的形态分布和形态转化。方法 采用电感耦合等离子体质谱分析转基因大豆富集前后硒的总量,采用蛋白酶提取,高效液相色谱-电感耦合等离子体质谱(high performance liquid chromatography-inductively coupled plasma-mass spectrometry,HPLC-ICP-MS)联用技术分析转基因大豆中的硒酸盐(selenate,Se VI)、亚硒酸盐(selenite,Se IV)、硒代蛋氨酸(selenomethionine,Se Met)和硒代胱氨酸(selenocystine,Se Cys)等几种硒化合物。盆栽种植试验研究转基因大豆对硒的富集作用。通过对照试验,考察大豆植株不同部位总硒含量变化和形态分布的转化情况。结果转基因大豆对硒有较好的富集作用,吸收的亚硒酸盐在大豆植株中部分转化成了硒代蛋氨酸和硒代胱氨酸。结论 了解了转基因大豆的形态分布和转化情况,可以更好地评估转基因大豆的食用安全风险并进行生物利用开发。     

Mercury and selenium concentrations in muscle tissue of different species of predatory freshwater fish and correlation between these elements

Concentrations of total mercury and selenium were determined in 49 and 42 muscle tissue samples, respectively, of six species of predatory freshwater fish, dace (Leuciscus leuciscus), pike perch (Sander lucioperca), pike (Esox lucius), European catfish (Silurus glanis), rainbow trout (Oncorhynchus mykiss) and asp (Aspius aspius). Muscle selenium concentration did not correlate with the corresponding total mercury concentration (R ^2?<?0.198) in all examined predatory fish species. There was an inverse correlation between the ratio Se/Hg content and the total mercury content in the muscle tissues of dace, pike perch, pike, European catfish and asp. The muscle tissue of rainbow trout exhibits a linear correlation between the ratio Se/Hg content and the total mercury content. The total mercury concentration of all examined samples did not exceed the hygienic limit for Hg for predatory fish.     

Bioefficacy of hydroxy-selenomethionine as a selenium supplement in pregnant dairy heifers and on the selenium status of their calves

This study aimed to determine the effects of supplementing pregnant heifers with the organic selenium (Se) source 2-hydroxy-4-methylselenobutanoic acid (HMSeBA) during the last 8 wk of pregnancy on dam and calf Se status. A total of 42 in-calf heifers were recruited to the study and randomly allocated to 1 of 3 treatments; a negative control (Con), sodium selenite (NaSe), or HMSeBA. Animals were blocked by body weight, body condition score, and expected calving date before treatment allocation. Following enrollment, all animals underwent a 7-wk wash-out period, after which they received their respective supplements, top-dressed daily onto a basal diet for the last 8 wk of pregnancy. Heifer blood samples were taken at weekly intervals from enrollment until 2 wk before expected calving date and as soon as possible after calving for determination of whole-blood glutathione peroxidase activity (GSH-Px) and plasma Se and malondialdehyde (MDA) concentrations. Selenized AA were determined in plasma samples taken at 3 wk precalving. A colostrum sample was taken as close to parturition as possible for determination of colostrum total Se, selenized AA, and IgG concentration. Calves were blood sampled as close to birth as possible for determination of whole-blood GSH-Px activity and plasma Se and MDA concentrations. Differences in whole-blood GSH-Px activity did not become apparent until calving; GSH-Px activity was lowest in Con heifers but similar between NaSe and HMSeBA heifers. Plasma Se was lowest in unsupplemented heifers and greatest in those supplemented with HMSeBA; this was attributable to greater selenomethionine concentrations in the plasma of HMSeBA heifers. Colostrum Se was lowest in Con heifers and greatest in HMSeBA heifers. The greater Se concentration of HMSeBA heifers was attributable to a greater proportion of total Se comprising selenocysteine; the reason for this is not known. There was no effect of supplementation on colostrum IgG concentration. Plasma Se was lowest in calves born to Con heifers and greatest in those born to HMSeBA heifers. There were no effects of treatment on calf whole-blood GSH-Px activity or plasma MDA concentration. The enhanced Se status associated with HMSeBA supplementation is likely a consequence of selenomethionine supply and may confer benefits to both the dam and her calf postpartum.     

Effects of washing pre-treatment on mercury concentration in fish tissue

The objective of this study was to examine the effect of washing pre-treatment on mercury concentration in fish fillet. Response surface methodology was used to investigate the influence of three variables, pH (1–6.5), NaCl (0–1% w/v) and exposure time (5–30 min) by using a three-factor central composite design. The aim was to obtain the best possible combination of these variables in order to reduce mercury in fish fillet. The experimental data were adequately fitted into a second-order polynomial model with multiple regression coefficients (R ²) of 0.961. The results indicated that the reduction of mercury in fish flesh significantly depends on the pH of the solution used. The overall optimal condition resulting in the maximum mercury reduction in fish fillet was obtained at a combined level pH of 2.79, NaCl of 0.5% and exposure time of 13.5 min. The optimized protocol produced a solution that can reduce mercury from raw fish fillet up to 81%.