Differences in mercury bioaccumulation between polar bears (Ursus maritimus) from the Canadian high- and sub-Arctic

Polar bears (Ursus maritimus) are being impacted by climate change and increased exposure to pollutants throughout their northern circumpolar range. In this study, we quantified concentrations of total mercury (THg) in the hair of polar bears from Canadian high- (southern Beaufort Sea, SBS) and sub- (western Hudson Bay, WHB) Arctic populations. Concentrations of THg in polar bears from the SBS population (14.8 ± 6.6 μg g(-1)) were significantly higher than in polar bears from WHB (4.1 ± 1.0 μg g(-1)). On the basis of δ(15)N signatures in hair, in conjunction with published δ(15)N signatures in particulate organic matter and sediments, we estimated that the pelagic and benthic food webs in the SBS are ～ 4.7 and ～ 4.0 trophic levels long, whereas in WHB they are only ～ 3.6 and ～ 3.3 trophic levels long. Furthermore, the more depleted δ(13)C ratios in hair from SBS polar bears relative to those from WHB suggests that SBS polar bears feed on food webs that are relatively more pelagic (and longer), whereas polar bears from WHB feed on those that are relatively more benthic (and shorter). Food web length and structure accounted for ～ 67% of the variation we found in THg concentrations among all polar bears across both populations. The regional difference in polar bear hair THg concentrations was also likely due to regional differences in water-column concentrations of methyl Hg (the toxic form of Hg that biomagnifies through food webs) available for bioaccumulation at the base of the food webs. For example, concentrations of methylated Hg at mid-depths in the marine water column of the northern Canadian Arctic Archipelago were 79.8 ± 37.3 pg L(-1), whereas, in HB, they averaged only 38.3 ± 16.6 pg L(-1). We conclude that a longer food web and higher pelagic concentrations of methylated Hg available to initiate bioaccumulation in the BS resulted in higher concentrations of THg in polar bears from the SBS region compared to those inhabiting the western coast of HB.     

Chemical composition of meat and blubber of the Cape fur seal (Arctocephalus pusillus pusillus)

Although the Cape fur seal is harvested commercially in southern Africa, no data exist to indicate whether its meat composition is such that it can be consumed by humans. Presently, these animals are harvested mainly for their hides. Little is known about the chemical composition of the meat and blubber and whether it could be processed into food or animal feed. This is the first report on the chemical composition of the Pectoralis muscle and fat of seal pups and bulls. The fat content in the muscle of pups was higher (4.2 g/100 g) than recorded in bulls (2.4 g/100 g). The protein content in muscle, on the other hand, was similar (23.2 g/100 g) for animals of both age groups. The blubber of bulls had a higher protein level (26.6 g/100 g) compared to that of pups (14.6 g/100 g), but a lower fat content (67.1 g/100 g vs 77.2 g/100 g). Muscle of bulls contained 33% saturated fatty acids (SFA), 29% monounsaturated fatty acids (MUFA) and 38% polyunsaturated fatty acids (PUFA). Muscle of pups contained 39% SFA, 30% MUFA and 31% PUFA. The toxin content in Cape fur seal blubber was lower than that reported for the blubber of Canadian seals. The organochlorine content in the blubber of Cape fur seals was lower than 13.7 ng/g oil, whereas levels as high as 87.2 ng/g have been reported in Canadian seal oil. The chemical composition of the Cape fur seal is such that it could be classified as a healthy meat source.     

Nutritional composition of blubber and meat of hooded seal (Cystophora cristata) and harp seal (Phagophilus groenlandicus) from Greenland

Seal blubber and skin are widely used, but the utilisation of blubber and meat for human consumption is limited. The aim of this study was to evaluate the nutritional composition of seal blubber and meat. The fatty acid composition, selected minerals and trace-elements, vitamins, amino acids and proximal composition of blubber and meat from hooded seal (Cystophora cristata) and harp seal (Phagophilus groenlandicus) from the “West Ice” near Greenland were analysed. The results showed that seal blubber is an excellent source of long- and very long-chain (VLC) n − 3 polyunsaturated fatty acids (PUFAs), in addition to long- and VLC monounsaturated fatty acids (MUFAs). Eicosapentaenoic acid (EPA) content contributed to a clear separation between blubber and meat from the two species. The blubber of harp seal showed the highest EPA (9.2%), whereas the muscle of harp seal showed the lowest EPA (3%) content. Seal meat is lean with less than 2% total fat, mainly composed of MUFAs, long- and VLC n − 3 PUFAs. In addition, the meat contains a high amount of proteins with a well-balanced amino acid composition. The trace-element content of seal meat is very high, particularly iron (379 μg/g muscle in hooded seal) and zinc (30 μg/g muscle in harp seal), as also is the vitamin content, especially vitamins A, D₃ and B₁₂. The seals included in this study varied greatly in age and size, which in turn may be the principal reason for the great individual variation observed in nutritional composition. On average, however, consumption of only 40 g seal meat covers the recommended daily intakes of iron and vitamin B₁₂ for young women. In conclusion, as long as the products fulfil the amending legislations regarding contaminants, both seal blubber and meat, from the present species, represent high quality food regarding nutrients and bioactive components beneficial for human health.     

Enantiomer-specific accumulation of PCB atropisomers in the bowhead whale (Balaena mysticetus)

Blubber (n = 40) and liver (n = 20) samples from the bowhead whale (Balaena mysticetus) were collected during the 1997-1998 Native (Inuit) subsistence harvests in Barrow, AK. Bowhead tissues and zooplankton were analyzed for polychlorinated biphenyl (PCB) concentrations and the enantiomeric fractions (EFs) of eight chiral PCB congeners (PCB-91, 95, 135, 136, 149, 174, 176, and 183) to quantify the enantiomer-specific accumulation of PCBs in this cetacean. PCB concentrations in bowhead blubber were low (mean +/- 1 SE: 610 +/- 54 ng g(-1) lipid) relative to other cetaceans. The accumulation of several chiral PCBs (PCB-91, 135, 149, 174, 176, and 183) in bowhead blubber was enantiomer-specific relative to bowhead liver and zooplankton, suggesting that biotransformation processes within the bowhead whale are enantioselective. The EFs for PCB-95 and 149 were significantly correlated with body length in male and female whales, while EFs for PCB-91 correlated with length in males only. Despite evidence for enantioselective biotransformation, all three congeners bioaccumulated in the bowhead relative to PCB-153. Results suggest that enantioselective accumulation of PCB-91, 95, and 149 is influenced by PCB concentrations, age, and/or the modification of an uncharacterized stereoselective process (or processes) during sexual maturity.     

Lipid metabolism, features of nutrition and risk factors of ischemic heart disease in cohorts of Canadian Inuits and Taimyr Nganasans]

Lipids metabolism and blood lipid profiles in native populations of Northern Asia (Nganasans, n = 43) and Northern Canada (Inuits, n = 151) have been studied. Estimation of serum PUFA of omega-6 and omega-3 series in Nganasans testifies to shifting of their diet to "western" type. Three types of dietary patterns have been observed in inuits: traditional one (among age group of 40-69), "western" (among age group of 18-29) and intermediate, transitional (among age group of 30-39). Age differences in concentrations of total cholesterol, summarized fraction of low density and very low density lipoproteins in Nganasans and Inuits were similar, however, Inuits had higher levels of blood lipids including HDL-cholesterol. Concentrations of apoB lipoproteins were significantly higher in Inuits, however, apoA-1/apoB ratios were estimated as more than 1.0 in both groups and the differences were not significant. Correlation between fatty acid composition and lipid profiles in Inuits who followed traditional diet testify to non-atherogenic type of nutrition. Despite to favorable blood lipid profiles in Northern native population, hypercholesterolemia was found in 2% of Nganasans and 10% of Inuits, while hypo-alpha-cholesterolemia was found in 25% Nganasans and in 5% of Inuits. Thus, changes in dietary patterns of native populations of the Far North have a great influence on blood concentrations of PUFAs of omega-3 series. Changes in the dietary fatty acid composition are considered to be one of the possible reasons of dislipoproteinemia.     

Congener-specific accumulation and food chain transfer of polybrominated diphenyl ethers in two arctic food chains

Congener-specific accumulation and prey to predator transfer of 22 polybrominated diphenyl ethers (PBDEs) were assessed in polar cod, ringed seal, polar bear, and beluga whale. Although the concentrations found were relatively low, these results show that PBDEs have reached the Arctic. PBDE congeners 47, 99, and 100 were dominant in all species studied. The pattern in ringed seal was somewhat simpler than in polar cod, with PBDE 47 accounting for more than 90% of the total PBDEs. In contrast, beluga whales, feeding on prey similar to that of ringed seals, showed higher PBDE levels and a more complex PBDE pattern than ringed seals. In contrast, polar bears contained only PBDE 47 in relatively small amounts. These differences in levels and patterns are likely due to species-specific differences in PBDE metabolism and accumulation. The metabolic index suggested that PBDEs 47 and 99 accumulate to the same magnitude as PCB 153 (PCB = polychlorinated biphenyl) in ringed seals and beluga whales. In contrast to beluga whales, ringed seals can metabolize PBDE 100 to some extent. Polar bears are seemingly capable of metabolizing virtually all PBDEs and are therefore unsuitable as indicators for PBDE contamination in the environment.     

Levels and temporal trends (1988-1999) of polybrominated diphenyl ethers in beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary, Canada

Polybrominated diphenyl ethers (PBDEs) were determined in blubber samples of 54 stranded adult beluga whales (Delphinapterus leucas) collected between 1988 and 1999 in the St. Lawrence Estuary (SLE), Quebec, Canada. Summed concentrations of 10 PBDE congeners (sigmaPBDEs) measured in beluga samples varied between 20 and almost 1000 ng/g wet weight. According to the PBDE concentrations in marine mammals reported in the scientific literature, SLE belugas appear to be relatively lightly contaminated. Only a few predominant congeners (namely, PBDE-47, -99, and -100) represent on average more than 75% of sigmaPBDEs in SLE belugas. The accumulation of sigmaPBDEs in both male and female belugas showed significant exponential increase throughout the 1988-1999 time period. The time necessary for beluga to double their blubber concentration of the most prevalent PBDE congeners was no longer than 3 years. The PBDE temporal changes reported in this study are generally faster but in agreement with the trend observed in other organisms collected in Canada, such as lake trout (Salvelinus namaycush) from the Great Lakes, ringed seal (Phoca hispida), and beluga whale from the Canadian Arctic. Some changes in the pattern of PBDEs in belugas were also observed during the time period investigated. The recent and important increase of PBDE levels in SLE belugas could explain the unexpected lack of statistical difference in PBDE contamination between males and females. This suggests that to date PBDEs tend to be accumulated by both male and female belugas, masking the elimination of PBDEs by females through post-natal transfer to their offspring. This study confirms that the growing use of PBDEs as flame retardants has resulted in rising contamination of Canadian aquatic environments. Additional studies are needed to assess the toxicological implications of the PBDE tissue levels found in SLE belugas.     

SEAL BLUBBER OIL: A NOVEL SOURCE OF ω3 FATTY ACIDS

Marine oils are perceived as having beneficial health effects since they prevent and treat cardiovascular diseases, among others. The ω3 polyunsaturated fatty acids have been recognized as an essential dietary component. Extensive studies on laboratory animals and human subjects have suggested that ω3 fatty acids may be included in the target tissues and cell membranes by dietary manipulation. The contribution of seal blubber to the total carcass weight is approximately 29% and it contains a high amount of long-chain ω3 fatty acids. Traditionally seal blubber oil has been used for industrial purposes, however, recent research findings have shown its potential application in foods as well as production of ω3 fatty acid concentrates. This review discusses production of concentrates from seal blubber oil.     

LIPOLYTIC ACTIVITY OF ENZYMES FROM GERMINATING SEEDS OF SESAME (SESAMUM INDICUM L.)

Sesame ( Sesumum indicum ) seeds were germinated for seven days under laboratory conditions and the lipolytic activity of the defatted, dried seedlings was determined. Germination increased the lipolytic activity of sesame seeds and the highest activity was observed on day-4. The lipases of four days germinated sesame seeds were able to hydrolyze mainly the saturated fatty acids from seal blubber oil (SBO). Reaction temperature, incubation period and oil-to-seedling powder ratio had a significant effect on the hydrolysis of saturated fatty acids, thereby concentrating unsaturated (mono- and polyunsaturated) fatty acids of seal blubber oil.     

EFFECT OF PROCESSING ON CONSTITUENTS AND OXIDATIVE STABILITY OF MARINE OILS

Changes in the contents of neutral and polar lipids, α-tocopherol, free fatty acids and color of seal blubber oil (SBO) and cod liver oil (CLO) during different processing steps of alkali-refining, bleaching, and deodorization were monitored. Refined, bleached and deodorized (RBD) SBO and CLO contained approximately 39 and 71% less polar lipids than their crude counterparts, respectively. There was also a reduction of 98.5 and 97.4% in the corresponding free fatty acids content of RBD-SBO and RBD-CLO. The content of α-tocopherol in both oils decreased during processing, especially at the bleaching and deodorization steps. The oxidative stability of SBO and CLO following each processing step was determined by measuring peroxide and 2-thiobarbituric acid reactive substances values. Results so obtained indicated that crude oils were most stable while their refined-bleached counterparts were least stable, perhaps due to the removal of endogenous natural antioxidants such as α-tocopherol during processing of oils.     

Polar lipids of water-melon (Citrullus vulgaris) and squash-melon (Citrullus vulgaris variety fistulosus) seeds

Qualitative and quantitative analysis of the polar ttpids in water-melon (Citrullus vulgaris) and squash, melon (Citrullus vulgaris variety fistulosus) is reported under the present study. Eight classes of polar ttpids, i.e. lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidylinositol, phosphatidyiethanolamine, phosphatidylglycerol, monogalactosyldiglyceride and phosphatidic acid have been identified. In both the species, phosphatidylcholine and phosphatidyl inositol formed the major portion of the ttpids. The squash-melon was found to contain a higher proportion of monogalactosyldiglycerides and phosphatidyl ethanolamine than water melon. Only a few fatty adds (palmitic, stearic, oleic and linoleic) were present in a measurable amount in the seed oils of these species with linoleic as the major and stearic as the minor one. There was great variation in the fatty add composition in different classes of polar lipids. The two species seem to be closely related to each other regarding their lipid make-up. They differ only in the fatty acid composition and the relative proportions of various classes of polar lipids.     

Oxidative stability of oil from blubber of harp seal (Phoca groenlandica) as assessed by NMR and standard procedures

Oils from seal blubber and cod liver were extracted, refined and bleached in a laboratory scale process. Oxidative stability of oils was evaluated over a 16-day period under accelerated oxidation conditions at 65°C. Peroxide value (PV), contents of conjugated dienes (CD) and trienes (CT), 2-thiobarbituric acid reactive substances (TBARS) and p-anisidine values (AnV) were determined. In addition, NMR spectroscopy was used to monitor relative changes in the proton pattern of the fatty acids of oils during storage. Cod liver oil showed higher PV, CD, CT and TBARS values as compared with seal blubber oil. The ratio of aliphatic to olefinic protons in both oils determined by NMR spectroscopy increased steadily over the entire length of the storage period, indicating progressive oxidation of unsaturated fatty acids in both oils. A significant correlation (P ≤0·05) was found between these ratios and TOTOX values (2PV + AnV) for both oils, thus suggesting that NMR methodology can be used as an effective means to simultaneously estimate both primary and secondary oxidation changes.     

Lipids and fatty acids of a whitefish (Coregonus albula) flesh and roe

The total lipids of whitefish flesh and roe averaged 3.0 and 9.8% fresh weight, respectively. Although neutral lipids dominated in both tissues the polar lipid content of fresh roe was unexceptionally high (2.5%). The fatty acid patterns of the total lipids from flesh and roe and of neutral lipids were similar to each other. Polyenoic acids constituted about half of the total fatty acids and monoenoic and saturated components existed in equal amounts. The calculated iodine values for the total lipids from flesh and roe indicated a slightly higher degree of unsaturation for roe fatty acids. The polar lipids were enriched in polyenoic and saturated fatty acids. Similarities in the composition and content of fatty acids from flesh and roe suggest that storage problems, apparent as a rancidity of roe products, may result from the high content of polar lipids readily hydrolysed during storage.     

Identification of marine mammal species in food products

Reference samples and processed products (frozen, smoked, salted, dried and gravad meat and blubber) from harp seal and minke, sei and fin whales were tested for species‐diagnostic molecular markers by random amplification of polymorphic DNA (RAPD) and single‐strand conformational polymorphism (SSCP) analysis of amplicons obtained using consensus primers for mitochondrial cytochrome b (mt cytb). RAPD analysis produced clear fingerprints of the products analysed from which the species could be easily identified. The interpretation of the SSCP analysis was less clear, probably owing to the use of consensus primers and, in fin whales, to intraspecific polymorphism. Except for one, all the commercial products were correctly labelled, and it was possible to identify the species in all the products labelled simply as ‘whale’: three of them contained minke whale and two fin whale. © 2000 Society of Chemical Industry     

Enzyme-catalyzed synthesis of structured lipids via acidolysis of seal (Phoca groenlandica) blubber oil with capric acid

A structured lipid (SL) containing n-3 fatty acids (eicosapentaenoic acid, 20:5n-3; docosahexaenoic acid, 22:6n-3) and capric acid (10:0; a medium chain fatty acid) was prepared using lipase-catalyzed acidolysis of seal blubber oil with capric acid. An immobilized lipase, Lipozyme-IM from Mucor miehei, was used as the biocatalyst. Acidolysis reactions were carried out in hexane and the products were analyzed by gas chromatography. Incorporation of capric acid was affected by mole ratio of substrates, type of organic solvent, reaction temperature, reaction time, water content and the amount of lipase. The optimum reaction mixture and conditions were oil/fatty acid mole ratio of 1:3, hexane, 45 °C, 24 h, 1% (w/w of substrates) water and 10% (w/w of substrates) Lipozyme-IM lipase. Under these conditions, a SL containing 2.3% 20:5n-3, 7.6% 22:6n-3 and 27.1% 10:0 was obtained. Solvents with log P values between 2.5 and 4.5 performed the acidolysis reaction better than those with log P values of less than 2.5. However, in the absence of any organic solvent, Lipozyme-IM afforded a satisfactory incorporation of capric acid into seal blubber oil.     

鲤、鲫卵的脂质和脂肪酸特性

鲤(Cyprinus carpio)、鲫(Carassius auratus)卵总脂分别为干基的16.90%和10.19%。两者脂质和脂肪酸组成总体比较接近。总脂中含较高的甘油三酯和极性脂,并含一定量的固醇及其酯。极性脂约占总脂的30%,主要为PC和PE,并含一定的心磷脂。两种鱼卵主要含C14～C22的19种脂肪酸,16:0和18:1含量最高,DHA等n-3族多烯酸和20:4n-6也较高,而EPA较低,P/S>>0.5。总脂中饱和、单不饱和、多不饱和脂肪酸的比例接近1:1:1,中性脂中C18、C20酸较多,极性脂中C22酸(DHA)较多。鲫卵18:2n-6较高,使得多烯酸含量稍高,胆固醇、磷脂含量及PC/PE和n-3/n-6稍低于鲤卵。研究表明:两种淡水鱼卵与其鱼肉相比,磷脂和胆固醇明显高,磷脂以PC为主,其次为PE;多烯酸稍高,其中DHA高而EPA低,并含20:4n-6。鲫卵PL的乳化稳定性低于相同浓度大豆磷脂的。其独特的脂质具有较大的研究利用价值。     

Isoprenoid fatty acids in antarctic krill (Euphausia superba)

In an attempt to elucidate the origin of phytanic (3,7,11,15-tetramethylhexadecanoic), pristanic (2,6,10,14-tetramethylpentadecanoic) and 4,8,12-trimethyltridecanoic acids found in small quantities in whales, the fatty acid composition of the lipids from Antarctic krill (Euphausia superba Dana) was determined by gas-liquid chromatography. Phytanic acid was found to be present to the extent of 1·4% of the total fatty acids, and was isolated and identified by mass and infra-red spectrometry. Two other isoprenoid fatty acids, pristanic acid (0·04%) and 4,8,12-trimethyltridecanoic acid (0·05%) were detected by gas-liquid chromatography. E. superba constitute almost exclusively the diet of whales inhabiting Antarctic waters, and the phytanic acid in whale oils is probably derived from ingested krill which presumably biosynthesise this acid from the phytol moiety of chlorophyll present in the diatoms on which these planktonic crustaceans live.     

Lipid quality and filleting yield of reared meagre (Argyrosomus regius)

Reared meagre (Argyrosomus regius) of average weight 1278 g was evaluated for its filleting yield and fillet lipid quality. Filleting yield averaged 42.2%, while very low levels of muscle fat deposits were measured (1.06%). Analysis of lipid classes revealed a high proportion of polar lipids (48.3–59.1%) and low levels of neutral fatty acids (40.9–51.7%) when compared to corresponding values of other farmed fish species. Phosphatidyl‐choline (PC) was the dominant polar lipid (2.92 mg g^?1 muscle), while cholesterol the most abundant neutral lipid (1.68 mg g^?1 muscle). The fatty acid composition of meagre fillet generally reflects the dietary fatty acids. Among n‐3 fatty acids, eicosapentaenoic (4.58%) and docohexaenoic (15.0%) were measured to be the most abundant ones, and 18:2n‐6 (11.9%) was the most common n‐6 fatty acid. The fatty acid profiles of polar and neutral fractions differ, with monounsaturated fatty acids being predominant in the neutral and n‐3 polyunsaturates in the polar lipids. The high polar lipid contents and n‐3 fatty acids and the low atherogenic and thrombogenic indexes indicate a high quality of this species’ lipids.