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See detailMobilisation of lipophilic pollutants from blubber in northern elephant seal pups (Mirounga angustirostris) during the post-weaning fast
Louis, Caroline; Dirtu, Alin C.; Stas, Marie et al

in Environmental Research (2014), 132

Northern elephant seals (NES) (Mirounga angustirostris) from the Año Nuevo State Reserve (CA, USA) were longitudinally sampled during the post-weaning fast in order to study the mobilisation and ... [more ▼]

Northern elephant seals (NES) (Mirounga angustirostris) from the Año Nuevo State Reserve (CA, USA) were longitudinally sampled during the post-weaning fast in order to study the mobilisation and redistribution of various classes of persistent organic pollutants (POPs), such as polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p′-DDE) and hexachlorobenzene (HCB) between blubber and blood. Inner and outer blubber layers were analysed separately. Organohalogenated compounds were detected in all blubber samples in the decreasing order of their concentrations: p,p′-DDE>PCBs⪢HCB>PBDEs. The concentrations of all studied compounds were homogeneously distributed in the blubber layer at early fast, since the concentrations of POPs were statistically not different in the inner and outer layers. With the progression of the fast, the concentrations of PBDEs, PCBs and p,p′-DDE increased more sharply in inner blubber than in outer blubber. As a result, their levels became significantly higher in inner blubber as compared to outer blubber at late fast. The rise of pollutant concentrations in blubber might result from a less efficient mobilisation than triglycerides and/or a reuptake by adipocytes of some of the pollutants released into the circulation. The mobilisation of pollutants from blubber was higher at late fast. An increase of pollutant concentrations was observed in serum between early and late fast. Lower halogenated congeners (i.e. tetra-CBs) were present in higher proportions in serum, whereas the higher halogenated congeners (i.e. hepta-CBs) were mainly found in the inner and outer blubber layers. The transfer ratios of both PBDEs and PCBs from inner blubber to serum decreased with the number of chlorine and bromine atoms. In addition, the distribution of both types of compounds between serum and blubber was strongly influenced by their lipophilic character (log Kow values), with more lipophilic compounds being less efficiently released from blubber to serum. [less ▲]

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See detailRelationships between in vitro lymphoproliferative responses and levels of contaminants in blood of free-ranging adult harbour seals (Phoca vitulina) from the North Sea
Dupont, Aurélie ULg; Siebert, Ursula; Covaci, Adrian et al

in Aquatic Toxicology (2013), 142-143

tIn vitro culture of peripheral blood leucocytes (PBLs) is currently used in toxicological studies of marinemammals. However, blood cells of wild individuals are exposed in vivo to environmental ... [more ▼]

tIn vitro culture of peripheral blood leucocytes (PBLs) is currently used in toxicological studies of marinemammals. However, blood cells of wild individuals are exposed in vivo to environmental contaminantsbefore being isolated and exposed to contaminants in vitro. The aim of this study was to highlightpotential relationships between blood contaminant levels and in vitro peripheral blood lymphocyteproliferation in free-ranging adult harbour seals (Phoca vitulina) from the North Sea. Blood samplesof 18 individuals were analyzed for trace elements (Fe, Zn, Se, Cu, Hg, Pb, Cd) and persistent organiccontaminants and metabolites ( PCBs, HO-PCBs, PBDEs, 2-MeO-BDE68 and 6-MeO-BDE47, DDXs,hexachlorobenzene, oxychlordane, trans-nonachlor, pentachlorophenol and tribromoanisole). The samesamples were used to determine the haematology profiles, cell numbers and viability, as well as thein vitro ConA-induced lymphocyte proliferation expressed as a stimulation index (SI). Correlation tests(Bravais-Pearson) and Principal Component Analysis with multiple regression revealed no statisticallysignificant relationship between the lymphocyte SI and the contaminants studied. However, the numberof lymphocytes per millilitre of whole blood appeared to be negatively correlated to pentachlorophenol(r = −0.63, p = 0.005). In adult harbour seals, the interindividual variations of in vitro lymphocyte pro-liferation did not appear to be directly linked to pollutant levels present in the blood, and it is likelythat other factors such as age, life history, or physiological parameters have an influence. In a generalmanner, experiments with in vitro immune cell cultures of wild marine mammals should be designed soas to minimize confounding factors in which case they remain a valuable tool to study pollutant effectsin vitro. [less ▲]

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See detailMercury in blood of free-ranging seals Phoca vitulina from the North Sea: Time-trend and association with environmental factors
Das, Krishna ULg; Brochoire, Charlène ULg; Chambosse, Mélanie et al

Conference (2012, March 27)

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment ... [more ▼]

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment. Recently, development of monitoring programs and non-invasive sampling techniques, including seal catches allowed blood sampling on a regular basis together with measurements of blubber thickness, body mass, sex and body length. Concentrations of total mercury (T-Hg) and other trace elements (Cd, Pb, Zn, Cu, Fe) as well as ∂13C and ∂15N values were determined by mass spectrometry in blood of 75 wild harbour seals caught in the German Wadden Sea between 1997 and 2011. ∂13C and ∂15N mean values (-17.5‰ and 18.1 ‰ respectively) were strongly similar to that measured previously in the muscle of stranded harbour seals from the Wadden Sea. In contrast, ∂15N mean value was strikingly higher than that recorded in grey seals (Halichoerus grypus) from Scotland (14.1 ‰ respectively; Habran et al. submitted.) while ∂13C values remained similar between the two seal species. These values confirmed the high trophic position of the harbour seal in the North Sea. In contrast to Cd and Pb, T-Hg in blood harbour seals reached concentrations as high as 2.1 μg.g-1 dry weight (10 times higher than the 0.21 μg.g-1 dry weight recorded for grey seals from Scotland) but depended on several factors including ∂15N values, age group and the body mass. T-Hg was detected in juveniles confirming maternal transfer to offspring and time-trend revealed no decrease of T-Hg in blood of harbour seals these last 15 years. [less ▲]

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See detailBlood dynamics of mercury and selenium in northern elephant seals during the lactation period
Habran, Sarah ULg; Debier, Cathy; Crocker, Dan et al

in Environmental Pollution (2011), 159(10), 2523-2529

The effects of reproduction and maternal investment (i.e., milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of mercury (Hg) and selenium ... [more ▼]

The effects of reproduction and maternal investment (i.e., milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of mercury (Hg) and selenium (Se) during lactation in the northern elephant seal (Mirounga angustirostris), a top predator from the North Pacific Ocean. Total Hg and Se levels were measured in whole blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. Both Hg and Se were transferred to offspring through the milk. Results suggested that the maternal transfer of Se was prominent during lactation, whereas the Hg transfer was larger during gestation. The lactation period affected Hg and Se levels in the blood of elephant seal mothers and pups. Physiological processes and their relationship to body condition should be considered carefully when interpreting trace element levels in the framework of biomonitoring. [less ▲]

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See detailPotential effects of blood contaminants on immune responses in harbour seals (Phoca vitulina)
Dupont, Aurélie ULg; Weijs, Liesbeth; Siebert, Ursula et al

Poster (2011, August 23)

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See detailDynamics of trace elements in grey seals throughout the lactation period
Habran, Sarah ULg; Pomeroy, P. P.; Debier, Cathy et al

Conference (2011, May 17)

The effects of reproduction and maternal investment (i.e. milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of Cd, Pb, Hg, Cr, Ni, V, Zn, Cu ... [more ▼]

The effects of reproduction and maternal investment (i.e. milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of Cd, Pb, Hg, Cr, Ni, V, Zn, Cu, Fe, Ca and Se throughout lactation in a top predator from the North Sea, the grey seal (Halichoerus grypus). Trace element levels were measured in blood and milk of 21 mother-pup pairs in early and late lactation. Maternal hair and natal fur (lanugo) were also collected and analyzed. Trace element levels in blood decreased according to the following pattern: Fe > Ca > Zn > Se > Cu > Hg > Pb > Cr > V in mothers and pups. Cd and Ni were not detected in blood. The substantial levels measured in lanugo indicate nevertheless that all trace elements (including Cd and Ni) were transferred to offspring through the placenta. In maternal hair, Pb levels (~ 2.2 mg/kg dw) were relatively high in comparison with other phocid species. All trace elements, except Cd, were detected in the milk showing a transmammary transfer to offspring, especially for elements such as Ca, Se, V, Ni and Pb. Hg showed the highest levels in blood (up to 0.25 mg/kg ww) and hair (up to 21 mg/kg dw) from the non-essential and toxic metals measured. Levels of Hg and essential elements (Ca, Fe, Zn, Cu and Se) in blood and milk showed significant variations throughout the lactation period. Therefore, physiological processes such as lactation affect trace element levels in tissues of mother and pup elephant seals. Such processes and its relationship to body condition should be considered carefully when interpreting trace element levels in the framework of biomonitoring. [less ▲]

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See detailThe harbor seal and the harbor porpoise from the North Sea: review of their ecotoxicological status based on stranded and free-ranging individuals and potential threaths to the population
Das, Krishna ULg; Weijs, Liesbeth; Habran, Sarah ULg et al

Conference (2011, May)

The harbor seal (Phoca vitulina) and the harbor porpoise (Phocoena phocoena) from the North Sea have experienced major fluctuations these last decades due to habitat loss, prey fluctuation and pollution ... [more ▼]

The harbor seal (Phoca vitulina) and the harbor porpoise (Phocoena phocoena) from the North Sea have experienced major fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment. Recently, development of monitoring programs and non-invasive sampling techniques, including seal catches in Germany allowed blood sampling together with measurements of blubber thickness, body mass, sex and body length. This approach is complementary to the study of stranded and by-caught individuals sampled during necropsies. Essential (Se, Zn, Cu, Fe) and non-essential elements (T-Hg, MeHg, Cd, Pb), perfluorinated organochemicals (PFCs) polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) were measured in blubber and in blood (for selected compounds) of stranded, by-caught and free-ranging individuals from Belgian and German coasts. In contrast to Cd and Pb, hepatic T-Hg can reach concentrations as high as 2.1 μg.g-1 dry weight but depended on several factors including position in the trophic chain (inferred from δ13C and δ15N values), age group and the body mass. This level has been shown to generate in vitro toxicity on harbor seal lymphocytes. Organic compound analysis (PFCs, PCBs, PBDEs) revealed widespread dispersion of contaminants in the marine environment with higher concentrations in seals compared to porpoises in agreement with the higher trophic position of the harbor seal. However, metabolization of these compounds differed between the two species, as revealed by the higher contribution of the persistent BDE-47 and lower chlorinated and non-persistent congeners (e.g. CB 52, CB95) in tissues of harbor porpoises. T-Hg, PFCs, PCBs and PBDEs were detected in calves confirming maternal transfer to offspring. These pollutants are strongly suspected to affect the immune and endocrine systems as well as vitamin A metabolism and this raises concern about exposure-related health effects, especially in younger individuals. [less ▲]

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See detailPOTENTIAL EFFECTS OF BLOOD CONTAMINANTS ON IMMUNE RESPONSES IN HARBOUR SEALS (PHOCA VITULINA)
Dupont, Aurélie ULg; Weijs, Liesbeth; Siebert, Ursula et al

in Organohalogen Compounds (2011), 73

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See detailMaternal transfer of PCBs, PBDEs and their hydroxylated metabolites in grey seal (Halichoerus grypus) from the Isle of May, Scotland
Vanden Berghe, Marie; Weijs, Liesbeth; Habran, Sarah ULg et al

in Organohalogen Compounds (2011)

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See detailAssessment of gestation, lactation and fasting on stable isotope ratios in northern elephant seals (Mirounga angustirostris)
Habran, Sarah ULg; Debier, Cathy; Crocker, Dan E. et al

in Marine Mammal Sciences (2010), 26(4), 880-895

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in ... [more ▼]

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long- and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring transfer of nutrients was generated between mother and offspring during gestation and lactation. This fractionation was tissue and time-specific, it varied between early and late lactation from +0.6‰ to +1.3‰ in blood cells and from +1.1‰ to nonsignificant value in serum. Therefore, if pups appear to be good proxies to investigate the female trophic ecology especially for C sources, much more caution is required in using δ15N values. Further studies are also needed to better define the relative impact of fasting and lactation on the enrichment or depletion of isotopes in different tissues. [less ▲]

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See detailMaternal transfer of trace metals to offspring in grey seals
Habran, Sarah ULg; Pomeroy, Paddy; Debier, Cathy et al

Conference (2010, May 25)

Marine mammals may display high heavy metal levels in their tissues, which raises the question of the importance of toxic metal transfer from mother to offspring. Some lactating female phocids fast during ... [more ▼]

Marine mammals may display high heavy metal levels in their tissues, which raises the question of the importance of toxic metal transfer from mother to offspring. Some lactating female phocids fast during the suckling period. This fasting period involves not only an important mobilization of energy reserves, but also mobilization of potentially associated contaminants. We studied maternal transfer of trace metals to offspring in the grey seal (Halichoerus grypus). Trace metal concentrations were measured in whole blood, milk and hair of mother-pup pairs in early and late lactation. Metal levels in blood decreased according to the following pattern: Fe > Zn > Se > Cu > Hg > Pb > Cr > V in mothers and pups. Cd and Ni were not detected and V, Cr and Pb levels were very low in maternal and pup blood. However, Ni and Pb levels were detected in the milk showing a transmammary transfer of these metals. Hg levels in blood and milk were higher than levels of previous metals and levels varied significantly throughout lactation. The increasing maternal levels over lactation were likely due to the remobilization of energy reserves during fasting and milk production in mothers causing a Hg release in blood. All metals were detected in hair and lanugo according to the following pattern: Fe > Zn > Hg > Cu > Se > Ni > V > Pb > Cd > Cr in mothers and Zn > Fe > Hg > Se > Cu > Pb > Ni > V > Cr > Cd in pups. Pb levels were relatively high in comparison with other phocid species. Only Hg showed a significant relationship between hair/lanugo and blood levels. This study highlights (i) a transplacental and transmammary transfer of metals in grey seals, and shows that (ii) physiological processes such as lactation and/or fasting can modify trace metal levels in the blood of mothers and pups. [less ▲]

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See detailRelationships between vitamin A and PCBs in grey seal mothers and pups during lactation
Vanden Berghe, Marie; Mat, Audrey; Arriola, Aline et al

in Environmental Pollution (2010), 158(5), 1570-1575

A previous study has shown a simultaneous increase of vitamin A and PCBs in grey seal (Halichoerus grypus) milk at late lactation (Debier et al., 2004). Here we sought to understand this unexpected ... [more ▼]

A previous study has shown a simultaneous increase of vitamin A and PCBs in grey seal (Halichoerus grypus) milk at late lactation (Debier et al., 2004). Here we sought to understand this unexpected relationship by comparing the dynamics of vitamin A and PCBs in the different tissue compartments of transfer. Lactating grey seals and their pups were sampled longitudinally in Scotland during the 2006 breeding season. As blubber reserves decreased, concentrations of vitamin A and PCBs increased during lactation in the inner layer of maternal blubber. A concomitant rise was observed in milk and consequently in the serum of suckling pups. The similar dynamics of vitamin A and PCBs in milk and inner blubber suggest a common mechanism of mobilisation from maternal body stores and transfer into the milk. A panel data analysis highlighted a negative impact of PCBs in milk and pup serum on vitamin A status in pup serum. © 2009 Elsevier Ltd. All rights reserved. [less ▲]

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See detailOrganochlorine pollutants in sea turtles and their association with vitamin A
Dyc, Christelle ULg; Debier, Cathy; Thomé, Jean-Pierre ULg et al

Poster (2010, May)

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See detailToxicodynamic of pollutants in poïkilotherm species
Dyc, Christelle ULg; Bouquegneau, Jean-Marie ULg; Debier, Cathy et al

Poster (2009, November 27)

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See detailMaternal transfer of mercury to offspring in phocids
Habran, Sarah ULg; Pomeroy, Paddy; Debier, Cathy et al

Conference (2009, June 09)

Marine mammals may display high mercury (Hg) levels in their tissues, which raises the question of the importance of toxic metal transfer from mother to offspring. Indeed, Hg could be transferred from ... [more ▼]

Marine mammals may display high mercury (Hg) levels in their tissues, which raises the question of the importance of toxic metal transfer from mother to offspring. Indeed, Hg could be transferred from mothers to fetuses via the placenta and to suckling pups via the milk, potentially affecting them during their most sensitive periods of development. Some lactating female phocids fast during the suckling period. This fasting period involves not only an important mobilization of energy reserves, but also mobilization of potentially associated contaminants. We studied and compared maternal transfer of Hg to offspring in two phocid species: the northern elephant seal (Mirounga angustirostris) from the Californian coast and the grey seal (Halichoerus grypus) from the Isle of May in Scotland. Total mercury concentrations (THg) were measured in whole blood and maternal milk of 20 mother-pup pairs of each species in early and late lactation. Methylmercury (MeHg) levels were also measured in the blood and milk of grey seals. Results indicated that Hg passed from the maternal tissue into the phocid milk. Milk showed a range of THg levels from 15 to 60 ppb (ng.g-1-wet-weight). From the first days after birth, pups displayed relatively high blood Hg levels suggesting that a Hg transfer through placenta occurred. Blood Hg levels in mothers and pups also varied significantly throughout lactation. While maternal levels doubled, pup levels were reduced by half between the beginning and the end of lactation. Remobilization of proteins and lipids during fasting and milk production in mothers might lead to a release of Hg in blood and therefore increase the levels in late lactation. On the contrary, Hg would be progressively stored in pup organs during their development. Decreasing Hg levels in pups also suggest that the Hg intake via the milk might be lower than that via the placenta. This study highlights a transplacental and transmammary transfer of Hg in both phocid populations. However, further toxicology studies are needed to help understand the potential impact of this Hg transfer. Results also showed that physiological processes such as lactation and/or fasting can modify Hg levels in the blood of mothers and pups. Therefore, such processes and body condition should be considered carefully when interpreting Hg levels in the framework of biomonitoring. [less ▲]

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See detailDevelopment of a strategy to study toxicodynamic of pollutants in spawning sea turtles from French West Indies (Guadeloupe and Martinique)
Dyc, Christelle ULg; Debier, Cathy; Thomé, Jean-Pierre ULg et al

Conference (2008, November)

Sea turtles including the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata are critically endangered species, facing different factors as marine pollution. There is a blatant ... [more ▼]

Sea turtles including the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata are critically endangered species, facing different factors as marine pollution. There is a blatant lack of data dealing with toxicants such as metals and persistent organic pollutants (POPs) in sea turtles. We developed a strategy to apprehend levels, effects and transfer to offspring of several pollutants in sea turtles. Sampling of blood, subcutaneous tissue and eggs of 15 gravid C. mydas and E. imbricata was carried out between July and September 2008 in Martinique (Diamant’s beach) and Guadeloupe (Petite Terre and Marie-Galante). Blood was collected from the dorso-cervical sinus and subcutaneous tissue was sampled in shoulder of the spawning females using a 5 mm biopsy punch (Kai Europe GmbH, Germany). Total blood and serum were successfully taken for metal, POP and biomarker investigations. T-mercury was analyzed by DMA milestones while PCBs, DDT and chlordecone were analyzed by EDC Ni63 high performance gas chromatography HPLC. Samples of serum were analyzed for vitamins (A and E) by HPLC and for thyroid hormones (triiodothyronine and thyroxine) by radioimmunoassay. In parallel to this field study, a cell model using 3T3-L1 cell line was built up to test in vitro effects of PCBs and mercury as well as the relationship between in vitro exposure and fat mobilization. Preliminary results showed a dose-response relationship between increased Aroclor 1234 and 1252 concentrations (0.5 ppb, 1 ppb and 1.5 ppb) and adipocyte mortality (Nucleocounter). The strategy we propose here will bring further insights on levels and potential impact of pollutants on female sea turtles and their offspring. [less ▲]

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See detailMaternal transfer of trace metals to offspring in northern elephant seals
Habran, Sarah ULg; Debier, Cathy; Crocker, Daniel et al

Poster (2008, October 30)

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See detailLactation effect on the trace element dynamics in northern elephant seals (Mirounga angustirostris)
Habran, Sarah ULg; Debier, Cathy; Lepoint, Gilles ULg et al

Conference (2007, November 30)

Northern elephant seals, Mirounga angustirostris, are exceptional mammals: females fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Females thus lose ... [more ▼]

Northern elephant seals, Mirounga angustirostris, are exceptional mammals: females fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Females thus lose approximately a third of body mass and produce energy-rich milk with a high fat content. Stable carbon and nitrogen isotope ratios (d13C and d15N used as diet markers) and total mercury concentrations (Hg) were measured in tissues (blood cells, serum, full blood, milk and blubber) from 20 mother-pup pairs on days 4 and 21 of lactation. A systematic difference was observed between isotopic values in blood cells and serum of the mothers, linked to diet and distinct biochemical composition between blood components. d13C differed between inner and outer blubber layers and were similar between inner blubber and milk. High Hg concentrations (up to 350 ng.g-1ww at the beginning of lactation) were found in the blood of mother elephant seals linked to their high d15N values in blood cells. Hg transfer through placenta and milk was observed between mothers and pups. A significant increase of blood Hg concentration in mothers (+285 ng.g-1ww) and a decrease in pups (-93 ng.g-1ww) were observed between days 4 and 21 of lactation. Both processes were explained by a remobilization of proteins and lipids during fasting and milk production in mothers and by a dilution of Hg in pups due to their high mass increase during this period. This study confirms that lactation modifies stable nitrogen isotope ratios in tissues, as well as mercury levels in blood from mothers and pups, and highlights the existence of a transplacental and transmammary transfer of mercury in northern elephant seals. Therefore, physiological processes and body condition should be considered carefully when interpreting stable isotope ratios and Hg concentrations in the framework of biomonitoring. [less ▲]

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See detailOrganochlorines and lactation : mobilization and transfer to offspring in northern elephant seals
Debier, Cathy; Crocker, D.; Xhonneux, V. et al

in Organohalogen Compounds (2007), 69

The transfer of PCBs and DDTs from mother to pup was studied in 20 Northern elephant seal Mirounga angustirostris mother-pup pairs. Organochlorine concentrations in milk increased from 127.3 ± 25.0 ng/g ... [more ▼]

The transfer of PCBs and DDTs from mother to pup was studied in 20 Northern elephant seal Mirounga angustirostris mother-pup pairs. Organochlorine concentrations in milk increased from 127.3 ± 25.0 ng/g to 200.9 ± 39.6 ng/g for PCBs and from 278.2 ± 92.4 ng/g to 494.9 ± 163.4 ng/g for DDTs between day 4 and day 21 of lactation. A similar longitudinal rise was observed in the serum of mothers (5.4 ± 0.8 to 7.7 ± 1.4 ng/ml for PCBs and 7.8 ± 2.4 to 11.9 ± 4.1 ng/ml for DDTs) and, to a lesser extend, in the serum of their pups (5.8 ± 1.4 to 6.1 ± 2.5 ng/ml for PCBs and 8.3 ± 2.5 to 9.9 ± 4.3 ng/ml for DDTs) between early and late lactation. The rise of contaminants in serum and milk might originate from the changes observed in maternal inner blubber in which PCB and DDT levels increased significantly throughout lactation (604.2 ± 142.8 to 1292.5 ± 421.6 ng/g lipids for PCBs and 1223.9 ± 460.0 to 2395.9 ± 737.3 ng/g lipids for DDTs). By contrast, contaminant levels remained constant in outer blubber (933.2 ± 271.8 to 999.7 ± 223.5 ng/g lipids for PCBs and 2010.7 ± 698.3 to 2061.9 ± 603.5 ng/g lipids for DDTs). [less ▲]

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